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	$242.93	5.450%	$256.1697	$256.17	$256.15	$256.20
Purchase #2	$197.74	4.209%	$206.0629	$206.06	$206.05	$206.10
Purchase #3	$53.54	10.787%	$59.3154	$59.32	$59.30	$59.30
Purchase #4	$78.63	5.424%	$82.8949	$82.89	$82.90	$82.90
Purchase #5	$172.92	12.821%	$195.0901	$195.09	$195.10	$195.10
Purchase #6	$172.92	10.750%	$191.5089	$191.51	$191.50	$191.50
Purchase #7	$37.98	11.581%	$42.3785	$42.38	$42.40	$42.40
7 purchase totals =	$956.66		$1,033.4204	$1,033.42	$1,033.40	$1,033.50