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	$40.68	11.333%	$45.2903	$45.29	$45.30	$45.30
Purchase #2	$28.42	5.388%	$29.9513	$29.95	$29.95	$30.00
Purchase #3	$78.36	4.621%	$81.981	$81.98	$82.00	$82.00
Purchase #4	$78.69	8.406%	$85.3047	$85.30	$85.30	$85.30
Purchase #5	$76.80	12.251%	$86.2088	$86.21	$86.20	$86.20
Purchase #6	$155.79	7.298%	$167.1596	$167.16	$167.15	$167.20
Purchase #7	$124.76	4.618%	$130.5214	$130.52	$130.50	$130.50
7 purchase totals =	$583.50		$626.4171	$626.41	$626.40	$626.50