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	$166.87	4.220%	$173.9119	$173.91	$173.90	$173.90
Purchase #2	$11.65	7.105%	$12.4777	$12.48	$12.50	$12.50
Purchase #3	$96.69	10.158%	$106.5118	$106.51	$106.50	$106.50
Purchase #4	$32.92	9.171%	$35.9391	$35.94	$35.95	$35.90
Purchase #5	$55.72	4.752%	$58.3678	$58.37	$58.35	$58.40
Purchase #6	$62.35	8.690%	$67.7682	$67.77	$67.75	$67.80
Purchase #7	$50.31	13.793%	$57.2493	$57.25	$57.25	$57.20
7 purchase totals =	$476.51		$512.2258	$512.23	$512.20	$512.20