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	$247.92	6.586%	$264.248	$264.25	$264.25	$264.20
Purchase #2	$212.47	12.248%	$238.4933	$238.49	$238.50	$238.50
Purchase #3	$88.36	11.522%	$98.5408	$98.54	$98.55	$98.50
Purchase #4	$50.45	5.235%	$53.0911	$53.09	$53.10	$53.10
Purchase #5	$55.27	6.719%	$58.9836	$58.98	$59.00	$59.00
Purchase #6	$104.43	4.453%	$109.0803	$109.08	$109.10	$109.10
Purchase #7	$177.47	3.310%	$183.3443	$183.34	$183.35	$183.30
7 purchase totals =	$936.37		$1,005.7814	$1,005.77	$1,005.85	$1,005.70