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	$84.52	7.413%	$90.7855	$90.79	$90.80	$90.80
Purchase #2	$44.41	13.821%	$50.5479	$50.55	$50.55	$50.50
Purchase #3	$205.44	5.389%	$216.5112	$216.51	$216.50	$216.50
Purchase #4	$250.74	6.261%	$266.4388	$266.44	$266.45	$266.40
Purchase #5	$101.99	8.754%	$110.9182	$110.92	$110.90	$110.90
Purchase #6	$216.56	11.606%	$241.694	$241.69	$241.70	$241.70
Purchase #7	$206.34	8.418%	$223.7097	$223.71	$223.70	$223.70
7 purchase totals =	$1,110.00		$1,200.6053	$1,200.61	$1,200.60	$1,200.50