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	$84.77	4.596%	$88.666	$88.67	$88.65	$88.70
Purchase #2	$138.34	8.549%	$150.1667	$150.17	$150.15	$150.20
Purchase #3	$53.91	9.110%	$58.8212	$58.82	$58.80	$58.80
Purchase #4	$39.69	9.631%	$43.5125	$43.51	$43.50	$43.50
Purchase #5	$199.74	11.710%	$223.1296	$223.13	$223.15	$223.10
Purchase #6	$105.25	9.777%	$115.5403	$115.54	$115.55	$115.50
Purchase #7	$74.96	10.607%	$82.911	$82.91	$82.90	$82.90
7 purchase totals =	$696.66		$762.7473	$762.75	$762.70	$762.70