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	$41.61	8.839%	$45.2879	$45.29	$45.30	$45.30
Purchase #2	$126.53	13.561%	$143.6887	$143.69	$143.70	$143.70
Purchase #3	$185.57	6.384%	$197.4168	$197.42	$197.40	$197.40
Purchase #4	$225.55	8.847%	$245.5044	$245.50	$245.50	$245.50
Purchase #5	$83.50	8.378%	$90.4956	$90.50	$90.50	$90.50
Purchase #6	$136.36	11.171%	$151.5928	$151.59	$151.60	$151.60
Purchase #7	$18.51	11.845%	$20.7025	$20.70	$20.70	$20.70
7 purchase totals =	$817.63		$894.6887	$894.69	$894.70	$894.70