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	$237.36	11.177%	$263.8897	$263.89	$263.90	$263.90
Purchase #2	$10.31	5.132%	$10.8391	$10.84	$10.85	$10.80
Purchase #3	$247.81	10.374%	$273.5178	$273.52	$273.50	$273.50
Purchase #4	$208.48	11.141%	$231.7068	$231.71	$231.70	$231.70
Purchase #5	$215.94	13.168%	$244.375	$244.38	$244.40	$244.40
Purchase #6	$215.84	6.218%	$229.2609	$229.26	$229.25	$229.30
Purchase #7	$140.87	5.690%	$148.8855	$148.89	$148.90	$148.90
7 purchase totals =	$1,276.61		$1,402.4748	$1,402.49	$1,402.50	$1,402.50