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	$185.73	5.797%	$196.4968	$196.50	$196.50	$196.50
Purchase #2	$126.78	4.777%	$132.8363	$132.84	$132.85	$132.80
Purchase #3	$235.72	11.635%	$263.146	$263.15	$263.15	$263.10
Purchase #4	$223.99	6.604%	$238.7823	$238.78	$238.80	$238.80
Purchase #5	$45.33	6.215%	$48.1473	$48.15	$48.15	$48.10
Purchase #6	$198.70	9.432%	$217.4414	$217.44	$217.45	$217.40
Purchase #7	$54.34	12.137%	$60.9352	$60.94	$60.95	$60.90
7 purchase totals =	$1,070.59		$1,157.7853	$1,157.80	$1,157.85	$1,157.60