Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$179.97	8.121%	$194.5854	$194.59	$194.60	$194.60
Purchase #2	$85.26	4.719%	$89.2834	$89.28	$89.30	$89.30
Purchase #3	$91.65	11.801%	$102.4656	$102.47	$102.45	$102.50
Purchase #4	$191.63	4.345%	$199.9563	$199.96	$199.95	$200.00
Purchase #5	$125.40	10.393%	$138.4328	$138.43	$138.45	$138.40
Purchase #6	$94.89	11.154%	$105.474	$105.47	$105.45	$105.50
Purchase #7	$203.30	8.644%	$220.8733	$220.87	$220.85	$220.90
7 purchase totals =	$972.10		$1,051.0708	$1,051.07	$1,051.05	$1,051.20