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	$58.32	5.420%	$61.4809	$61.48	$61.50	$61.50
Purchase #2	$37.83	10.630%	$41.8513	$41.85	$41.85	$41.90
Purchase #3	$110.75	11.225%	$123.1817	$123.18	$123.20	$123.20
Purchase #4	$71.97	8.568%	$78.1364	$78.14	$78.15	$78.10
Purchase #5	$220.64	13.178%	$249.7159	$249.72	$249.70	$249.70
Purchase #6	$185.51	4.848%	$194.5035	$194.50	$194.50	$194.50
Purchase #7	$6.34	9.559%	$6.946	$6.95	$6.95	$6.90
7 purchase totals =	$691.36		$755.8157	$755.82	$755.85	$755.80