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	$40.78	11.744%	$45.5692	$45.57	$45.55	$45.60
Purchase #2	$227.51	7.650%	$244.9145	$244.91	$244.90	$244.90
Purchase #3	$9.36	11.713%	$10.4563	$10.46	$10.45	$10.50
Purchase #4	$154.90	11.854%	$173.2618	$173.26	$173.25	$173.30
Purchase #5	$182.28	3.306%	$188.3062	$188.31	$188.30	$188.30
Purchase #6	$161.70	12.584%	$182.0483	$182.05	$182.05	$182.00
Purchase #7	$100.49	10.509%	$111.0505	$111.05	$111.05	$111.10
7 purchase totals =	$877.02		$955.6068	$955.61	$955.55	$955.70