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	$84.43	5.830%	$89.3523	$89.35	$89.35	$89.40
Purchase #2	$48.98	9.215%	$53.4935	$53.49	$53.50	$53.50
Purchase #3	$230.83	5.170%	$242.7639	$242.76	$242.75	$242.80
Purchase #4	$230.35	11.339%	$256.4694	$256.47	$256.45	$256.50
Purchase #5	$44.88	9.619%	$49.197	$49.20	$49.20	$49.20
Purchase #6	$89.99	6.484%	$95.825	$95.83	$95.85	$95.80
Purchase #7	$225.77	4.684%	$236.3451	$236.35	$236.35	$236.30
7 purchase totals =	$955.23		$1,023.4462	$1,023.45	$1,023.45	$1,023.50