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	$9.33	10.723%	$10.3305	$10.33	$10.35	$10.30
Purchase #2	$228.72	5.130%	$240.4533	$240.45	$240.45	$240.50
Purchase #3	$174.67	12.709%	$196.8688	$196.87	$196.85	$196.90
Purchase #4	$62.92	11.319%	$70.0419	$70.04	$70.05	$70.00
Purchase #5	$15.93	12.274%	$17.8852	$17.89	$17.90	$17.90
Purchase #6	$156.30	11.512%	$174.2933	$174.29	$174.30	$174.30
Purchase #7	$197.62	12.180%	$221.6901	$221.69	$221.70	$221.70
7 purchase totals =	$845.49		$931.5631	$931.56	$931.60	$931.60