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	$165.87	6.365%	$176.4276	$176.43	$176.45	$176.40
Purchase #2	$93.51	13.157%	$105.8131	$105.81	$105.80	$105.80
Purchase #3	$78.31	6.833%	$83.6609	$83.66	$83.65	$83.70
Purchase #4	$62.93	13.433%	$71.3834	$71.38	$71.40	$71.40
Purchase #5	$196.86	12.221%	$220.9183	$220.92	$220.90	$220.90
Purchase #6	$224.99	8.237%	$243.5224	$243.52	$243.50	$243.50
Purchase #7	$149.89	5.727%	$158.4742	$158.47	$158.45	$158.50
7 purchase totals =	$972.36		$1,060.1999	$1,060.19	$1,060.15	$1,060.20