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	$81.54	12.449%	$91.6909	$91.69	$91.70	$91.70
Purchase #2	$118.75	4.262%	$123.8111	$123.81	$123.80	$123.80
Purchase #3	$170.65	4.232%	$177.8719	$177.87	$177.85	$177.90
Purchase #4	$150.38	11.355%	$167.4556	$167.46	$167.45	$167.50
Purchase #5	$10.90	13.688%	$12.392	$12.39	$12.40	$12.40
Purchase #6	$61.83	13.263%	$70.0305	$70.03	$70.05	$70.00
Purchase #7	$77.81	13.685%	$88.4583	$88.46	$88.45	$88.50
7 purchase totals =	$671.86		$731.7103	$731.71	$731.70	$731.80