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	$233.64	4.400%	$243.9202	$243.92	$243.90	$243.90
Purchase #2	$18.78	8.689%	$20.4118	$20.41	$20.40	$20.40
Purchase #3	$74.81	4.773%	$78.3807	$78.38	$78.40	$78.40
Purchase #4	$249.67	5.130%	$262.4781	$262.48	$262.50	$262.50
Purchase #5	$148.47	7.457%	$159.5414	$159.54	$159.55	$159.50
Purchase #6	$13.41	7.173%	$14.3719	$14.37	$14.35	$14.40
Purchase #7	$223.85	13.369%	$253.7765	$253.78	$253.80	$253.80
7 purchase totals =	$962.63		$1,032.8806	$1,032.88	$1,032.90	$1,032.90