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	$200.38	4.170%	$208.7358	$208.74	$208.75	$208.70
Purchase #2	$156.29	8.426%	$169.459	$169.46	$169.45	$169.50
Purchase #3	$88.78	7.606%	$95.5326	$95.53	$95.55	$95.50
Purchase #4	$65.36	9.198%	$71.3718	$71.37	$71.35	$71.40
Purchase #5	$245.57	12.310%	$275.7997	$275.80	$275.80	$275.80
Purchase #6	$180.69	6.651%	$192.7077	$192.71	$192.70	$192.70
Purchase #7	$57.94	6.339%	$61.6128	$61.61	$61.60	$61.60
7 purchase totals =	$995.01		$1,075.2194	$1,075.22	$1,075.20	$1,075.20