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	$205.90	6.176%	$218.6164	$218.62	$218.60	$218.60
Purchase #2	$80.69	12.555%	$90.8206	$90.82	$90.80	$90.80
Purchase #3	$247.71	6.171%	$262.9962	$263.00	$263.00	$263.00
Purchase #4	$59.89	11.822%	$66.9702	$66.97	$66.95	$67.00
Purchase #5	$69.51	10.123%	$76.5465	$76.55	$76.55	$76.50
Purchase #6	$151.86	12.391%	$170.677	$170.68	$170.70	$170.70
Purchase #7	$71.41	10.140%	$78.651	$78.65	$78.65	$78.70
7 purchase totals =	$886.97		$965.2779	$965.29	$965.25	$965.30