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	$74.88	13.562%	$85.0352	$85.04	$85.05	$85.00
Purchase #2	$127.29	4.864%	$133.4814	$133.48	$133.50	$133.50
Purchase #3	$8.65	13.797%	$9.8434	$9.84	$9.85	$9.80
Purchase #4	$65.40	9.109%	$71.3573	$71.36	$71.35	$71.40
Purchase #5	$39.54	13.386%	$44.8328	$44.83	$44.85	$44.80
Purchase #6	$238.86	5.262%	$251.4288	$251.43	$251.45	$251.40
Purchase #7	$248.85	7.142%	$266.6229	$266.62	$266.60	$266.60
7 purchase totals =	$803.47		$862.6018	$862.60	$862.65	$862.50