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	$69.48	12.185%	$77.9461	$77.95	$77.95	$77.90
Purchase #2	$51.78	3.843%	$53.7699	$53.77	$53.75	$53.80
Purchase #3	$40.38	9.404%	$44.1773	$44.18	$44.20	$44.20
Purchase #4	$50.27	9.131%	$54.8602	$54.86	$54.85	$54.90
Purchase #5	$230.64	12.795%	$260.1504	$260.15	$260.15	$260.20
Purchase #6	$61.50	6.195%	$65.3099	$65.31	$65.30	$65.30
Purchase #7	$169.57	9.533%	$185.7351	$185.74	$185.75	$185.70
7 purchase totals =	$673.62		$741.9489	$741.96	$741.95	$742.00