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	$81.89	12.513%	$92.1369	$92.14	$92.15	$92.10
Purchase #2	$32.84	13.126%	$37.1506	$37.15	$37.15	$37.20
Purchase #3	$91.29	6.113%	$96.8706	$96.87	$96.85	$96.90
Purchase #4	$126.73	3.484%	$131.1453	$131.15	$131.15	$131.10
Purchase #5	$111.47	13.200%	$126.184	$126.18	$126.20	$126.20
Purchase #6	$91.93	13.464%	$104.3075	$104.31	$104.30	$104.30
Purchase #7	$34.80	13.352%	$39.4465	$39.45	$39.45	$39.40
7 purchase totals =	$570.95		$627.2414	$627.25	$627.25	$627.20