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	$135.81	12.242%	$152.4359	$152.44	$152.45	$152.40
Purchase #2	$172.85	11.204%	$192.2161	$192.22	$192.20	$192.20
Purchase #3	$175.82	7.311%	$188.6742	$188.67	$188.65	$188.70
Purchase #4	$88.83	7.490%	$95.4834	$95.48	$95.50	$95.50
Purchase #5	$71.45	10.460%	$78.9237	$78.92	$78.90	$78.90
Purchase #6	$199.51	8.133%	$215.7361	$215.74	$215.75	$215.70
Purchase #7	$77.93	12.754%	$87.8692	$87.87	$87.85	$87.90
7 purchase totals =	$922.20		$1,011.3386	$1,011.34	$1,011.30	$1,011.30