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	$65.89	10.274%	$72.6595	$72.66	$72.65	$72.70
Purchase #2	$250.78	11.467%	$279.5369	$279.54	$279.55	$279.50
Purchase #3	$177.30	8.795%	$192.8935	$192.89	$192.90	$192.90
Purchase #4	$244.77	12.318%	$274.9208	$274.92	$274.90	$274.90
Purchase #5	$248.26	4.731%	$260.0052	$260.01	$260.00	$260.00
Purchase #6	$98.76	12.466%	$111.0714	$111.07	$111.05	$111.10
Purchase #7	$147.77	12.123%	$165.6842	$165.68	$165.70	$165.70
7 purchase totals =	$1,233.53		$1,356.7715	$1,356.77	$1,356.75	$1,356.80