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	$140.43	8.490%	$152.3525	$152.35	$152.35	$152.40
Purchase #2	$182.57	4.160%	$190.1649	$190.16	$190.15	$190.20
Purchase #3	$130.78	4.858%	$137.1333	$137.13	$137.15	$137.10
Purchase #4	$245.47	9.664%	$269.1922	$269.19	$269.20	$269.20
Purchase #5	$70.95	10.182%	$78.1741	$78.17	$78.15	$78.20
Purchase #6	$9.64	9.609%	$10.5663	$10.57	$10.55	$10.60
Purchase #7	$241.34	6.279%	$256.4937	$256.49	$256.50	$256.50
7 purchase totals =	$1,021.18		$1,094.0770	$1,094.06	$1,094.05	$1,094.20