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	$83.36	11.707%	$93.119	$93.12	$93.10	$93.10
Purchase #2	$222.94	4.721%	$233.465	$233.47	$233.45	$233.50
Purchase #3	$11.50	7.374%	$12.348	$12.35	$12.35	$12.30
Purchase #4	$245.73	12.445%	$276.3111	$276.31	$276.30	$276.30
Purchase #5	$231.73	4.221%	$241.5113	$241.51	$241.50	$241.50
Purchase #6	$101.30	9.571%	$110.9954	$111.00	$111.00	$111.00
Purchase #7	$167.74	13.476%	$190.3446	$190.34	$190.35	$190.30
7 purchase totals =	$1,064.30		$1,158.0944	$1,158.10	$1,158.05	$1,158.00