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	$178.68	10.218%	$196.9375	$196.94	$196.95	$196.90
Purchase #2	$13.57	11.468%	$15.1262	$15.13	$15.15	$15.10
Purchase #3	$20.31	9.738%	$22.2878	$22.29	$22.30	$22.30
Purchase #4	$125.65	5.827%	$132.9716	$132.97	$132.95	$133.00
Purchase #5	$33.77	5.741%	$35.7087	$35.71	$35.70	$35.70
Purchase #6	$134.31	10.446%	$148.34	$148.34	$148.35	$148.30
Purchase #7	$12.88	11.131%	$14.3137	$14.31	$14.30	$14.30
7 purchase totals =	$519.17		$565.6855	$565.69	$565.70	$565.60