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	$222.62	12.780%	$251.0708	$251.07	$251.05	$251.10
Purchase #2	$106.52	9.823%	$116.9835	$116.98	$117.00	$117.00
Purchase #3	$45.76	7.388%	$49.1407	$49.14	$49.15	$49.10
Purchase #4	$35.94	6.768%	$38.3724	$38.37	$38.35	$38.40
Purchase #5	$157.93	12.638%	$177.8892	$177.89	$177.90	$177.90
Purchase #6	$134.37	12.616%	$151.3221	$151.32	$151.30	$151.30
Purchase #7	$246.47	12.447%	$277.1481	$277.15	$277.15	$277.10
7 purchase totals =	$949.61		$1,061.9268	$1,061.92	$1,061.90	$1,061.90