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	$234.43	8.415%	$254.1573	$254.16	$254.15	$254.20
Purchase #2	$37.68	3.708%	$39.0772	$39.08	$39.10	$39.10
Purchase #3	$137.31	10.309%	$151.4653	$151.47	$151.45	$151.50
Purchase #4	$93.63	9.463%	$102.4902	$102.49	$102.50	$102.50
Purchase #5	$178.91	5.339%	$188.462	$188.46	$188.45	$188.50
Purchase #6	$233.80	12.517%	$263.0647	$263.06	$263.05	$263.10
Purchase #7	$161.77	4.341%	$168.7924	$168.79	$168.80	$168.80
7 purchase totals =	$1,077.53		$1,167.5091	$1,167.51	$1,167.50	$1,167.70