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	$185.34	3.681%	$192.1624	$192.16	$192.15	$192.20
Purchase #2	$202.91	11.240%	$225.7171	$225.72	$225.70	$225.70
Purchase #3	$179.78	6.127%	$190.7951	$190.80	$190.80	$190.80
Purchase #4	$21.33	4.414%	$22.2715	$22.27	$22.25	$22.30
Purchase #5	$203.42	9.468%	$222.6798	$222.68	$222.70	$222.70
Purchase #6	$180.95	8.340%	$196.0412	$196.04	$196.05	$196.00
Purchase #7	$68.57	7.407%	$73.649	$73.65	$73.65	$73.60
7 purchase totals =	$1,042.30		$1,123.3161	$1,123.32	$1,123.30	$1,123.30