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	$93.28	11.751%	$104.2413	$104.24	$104.25	$104.20
Purchase #2	$169.35	10.274%	$186.749	$186.75	$186.75	$186.70
Purchase #3	$212.59	13.302%	$240.8687	$240.87	$240.85	$240.90
Purchase #4	$187.53	9.830%	$205.9642	$205.96	$205.95	$206.00
Purchase #5	$11.77	5.188%	$12.3806	$12.38	$12.40	$12.40
Purchase #6	$65.43	9.211%	$71.4568	$71.46	$71.45	$71.50
Purchase #7	$11.57	7.870%	$12.4806	$12.48	$12.50	$12.50
7 purchase totals =	$751.52		$834.1412	$834.14	$834.15	$834.20