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	$137.92	12.269%	$154.8414	$154.84	$154.85	$154.80
Purchase #2	$215.60	12.375%	$242.2805	$242.28	$242.30	$242.30
Purchase #3	$243.29	7.528%	$261.6049	$261.60	$261.60	$261.60
Purchase #4	$226.54	7.727%	$244.0447	$244.04	$244.05	$244.00
Purchase #5	$99.67	11.623%	$111.2546	$111.25	$111.25	$111.30
Purchase #6	$217.51	7.188%	$233.1446	$233.14	$233.15	$233.10
Purchase #7	$185.82	6.807%	$198.4688	$198.47	$198.45	$198.50
7 purchase totals =	$1,326.35		$1,445.6395	$1,445.62	$1,445.65	$1,445.60