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	$62.27	5.413%	$65.6407	$65.64	$65.65	$65.60
Purchase #2	$216.25	13.650%	$245.7681	$245.77	$245.75	$245.80
Purchase #3	$26.85	3.253%	$27.7234	$27.72	$27.70	$27.70
Purchase #4	$121.25	8.479%	$131.5308	$131.53	$131.55	$131.50
Purchase #5	$50.29	10.536%	$55.5886	$55.59	$55.60	$55.60
Purchase #6	$81.44	9.201%	$88.9333	$88.93	$88.95	$88.90
Purchase #7	$176.48	11.590%	$196.934	$196.93	$196.95	$196.90
7 purchase totals =	$734.83		$812.1189	$812.11	$812.15	$812.00