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	$53.68	10.746%	$59.4485	$59.45	$59.45	$59.40
Purchase #2	$41.84	9.668%	$45.8851	$45.89	$45.90	$45.90
Purchase #3	$237.32	7.111%	$254.1958	$254.20	$254.20	$254.20
Purchase #4	$48.30	12.488%	$54.3317	$54.33	$54.35	$54.30
Purchase #5	$100.29	8.851%	$109.1667	$109.17	$109.15	$109.20
Purchase #6	$5.95	11.793%	$6.6517	$6.65	$6.65	$6.70
Purchase #7	$199.97	4.268%	$208.5047	$208.50	$208.50	$208.50
7 purchase totals =	$687.35		$738.1842	$738.19	$738.20	$738.20