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	$57.33	12.528%	$64.5123	$64.51	$64.50	$64.50
Purchase #2	$86.58	10.745%	$95.883	$95.88	$95.90	$95.90
Purchase #3	$103.63	6.815%	$110.6924	$110.69	$110.70	$110.70
Purchase #4	$68.72	13.864%	$78.2473	$78.25	$78.25	$78.20
Purchase #5	$52.42	3.290%	$54.1446	$54.14	$54.15	$54.10
Purchase #6	$126.54	7.609%	$136.1684	$136.17	$136.15	$136.20
Purchase #7	$146.67	6.725%	$156.5336	$156.53	$156.55	$156.50
7 purchase totals =	$641.89		$696.1816	$696.17	$696.20	$696.10