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	$103.87	9.338%	$113.5694	$113.57	$113.55	$113.60
Purchase #2	$35.62	9.442%	$38.9832	$38.98	$39.00	$39.00
Purchase #3	$35.95	11.563%	$40.1069	$40.11	$40.10	$40.10
Purchase #4	$136.78	10.681%	$151.3895	$151.39	$151.40	$151.40
Purchase #5	$144.91	10.378%	$159.9488	$159.95	$159.95	$159.90
Purchase #6	$33.60	10.635%	$37.1734	$37.17	$37.15	$37.20
Purchase #7	$206.55	7.742%	$222.5411	$222.54	$222.55	$222.50
7 purchase totals =	$697.28		$763.7123	$763.71	$763.70	$763.70