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	$77.47	7.251%	$83.0873	$83.09	$83.10	$83.10
Purchase #2	$246.78	11.683%	$275.6113	$275.61	$275.60	$275.60
Purchase #3	$165.25	7.759%	$178.0717	$178.07	$178.05	$178.10
Purchase #4	$54.69	8.495%	$59.3359	$59.34	$59.35	$59.30
Purchase #5	$64.36	13.872%	$73.288	$73.29	$73.30	$73.30
Purchase #6	$171.29	4.742%	$179.4126	$179.41	$179.40	$179.40
Purchase #7	$193.40	5.323%	$203.6947	$203.69	$203.70	$203.70
7 purchase totals =	$973.24		$1,052.5015	$1,052.50	$1,052.50	$1,052.50