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	$112.62	6.189%	$119.5901	$119.59	$119.60	$119.60
Purchase #2	$84.82	6.275%	$90.1425	$90.14	$90.15	$90.10
Purchase #3	$133.84	12.259%	$150.2474	$150.25	$150.25	$150.20
Purchase #4	$165.52	7.587%	$178.078	$178.08	$178.10	$178.10
Purchase #5	$173.72	6.583%	$185.156	$185.16	$185.15	$185.20
Purchase #6	$128.70	8.377%	$139.4812	$139.48	$139.50	$139.50
Purchase #7	$223.74	13.310%	$253.5198	$253.52	$253.50	$253.50
7 purchase totals =	$1,022.96		$1,116.2150	$1,116.22	$1,116.25	$1,116.20