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	$103.33	5.816%	$109.3397	$109.34	$109.35	$109.30
Purchase #2	$191.81	13.495%	$217.6948	$217.69	$217.70	$217.70
Purchase #3	$32.62	10.779%	$36.1361	$36.14	$36.15	$36.10
Purchase #4	$166.90	12.801%	$188.2649	$188.26	$188.25	$188.30
Purchase #5	$54.98	6.262%	$58.4228	$58.42	$58.40	$58.40
Purchase #6	$152.59	3.827%	$158.4296	$158.43	$158.45	$158.40
Purchase #7	$30.83	7.832%	$33.2446	$33.24	$33.25	$33.20
7 purchase totals =	$733.06		$801.5325	$801.52	$801.55	$801.40