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	$227.38	4.428%	$237.4484	$237.45	$237.45	$237.40
Purchase #2	$48.63	6.707%	$51.8916	$51.89	$51.90	$51.90
Purchase #3	$218.30	4.505%	$228.1344	$228.13	$228.15	$228.10
Purchase #4	$15.32	9.747%	$16.8132	$16.81	$16.80	$16.80
Purchase #5	$130.76	6.816%	$139.6726	$139.67	$139.65	$139.70
Purchase #6	$78.85	9.777%	$86.5592	$86.56	$86.55	$86.60
Purchase #7	$151.72	13.810%	$172.6725	$172.67	$172.65	$172.70
7 purchase totals =	$870.96		$933.1919	$933.18	$933.15	$933.20