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	$79.38	5.325%	$83.607	$83.61	$83.60	$83.60
Purchase #2	$67.30	5.254%	$70.8359	$70.84	$70.85	$70.80
Purchase #3	$50.41	7.195%	$54.037	$54.04	$54.05	$54.00
Purchase #4	$250.30	9.642%	$274.4339	$274.43	$274.45	$274.40
Purchase #5	$170.34	5.300%	$179.368	$179.37	$179.35	$179.40
Purchase #6	$230.31	11.723%	$257.3092	$257.31	$257.30	$257.30
Purchase #7	$43.45	12.619%	$48.933	$48.93	$48.95	$48.90
7 purchase totals =	$891.49		$968.5240	$968.53	$968.55	$968.40