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	$86.69	3.310%	$89.5594	$89.56	$89.55	$89.60
Purchase #2	$79.47	8.140%	$85.9389	$85.94	$85.95	$85.90
Purchase #3	$140.71	9.836%	$154.5502	$154.55	$154.55	$154.60
Purchase #4	$41.26	12.784%	$46.5347	$46.53	$46.55	$46.50
Purchase #5	$26.66	10.599%	$29.4857	$29.49	$29.50	$29.50
Purchase #6	$223.31	3.812%	$231.8226	$231.82	$231.80	$231.80
Purchase #7	$71.29	7.693%	$76.7743	$76.77	$76.75	$76.80
7 purchase totals =	$669.39		$714.6658	$714.66	$714.65	$714.70