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	$130.58	8.217%	$141.3098	$141.31	$141.30	$141.30
Purchase #2	$87.89	12.182%	$98.5968	$98.60	$98.60	$98.60
Purchase #3	$89.37	5.251%	$94.0628	$94.06	$94.05	$94.10
Purchase #4	$60.60	11.717%	$67.7005	$67.70	$67.70	$67.70
Purchase #5	$134.63	10.643%	$148.9587	$148.96	$148.95	$149.00
Purchase #6	$25.72	10.403%	$28.3957	$28.40	$28.40	$28.40
Purchase #7	$206.51	7.772%	$222.56	$222.56	$222.55	$222.60
7 purchase totals =	$735.30		$801.5843	$801.59	$801.55	$801.70