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	$201.31	3.455%	$208.2653	$208.27	$208.25	$208.30
Purchase #2	$215.84	10.346%	$238.1708	$238.17	$238.15	$238.20
Purchase #3	$179.59	9.388%	$196.4499	$196.45	$196.45	$196.40
Purchase #4	$248.68	10.471%	$274.7193	$274.72	$274.70	$274.70
Purchase #5	$204.33	12.616%	$230.1083	$230.11	$230.10	$230.10
Purchase #6	$69.50	8.592%	$75.4714	$75.47	$75.45	$75.50
Purchase #7	$37.89	8.578%	$41.1402	$41.14	$41.15	$41.10
7 purchase totals =	$1,157.14		$1,264.3252	$1,264.33	$1,264.25	$1,264.30