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	$144.94	13.109%	$163.9402	$163.94	$163.95	$163.90
Purchase #2	$68.64	3.596%	$71.1083	$71.11	$71.10	$71.10
Purchase #3	$60.64	3.546%	$62.7903	$62.79	$62.80	$62.80
Purchase #4	$204.38	10.274%	$225.378	$225.38	$225.40	$225.40
Purchase #5	$185.47	5.862%	$196.3423	$196.34	$196.35	$196.30
Purchase #6	$170.76	11.363%	$190.1635	$190.16	$190.15	$190.20
Purchase #7	$240.45	7.610%	$258.7482	$258.75	$258.75	$258.70
7 purchase totals =	$1,075.28		$1,168.4708	$1,168.47	$1,168.50	$1,168.40