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	$48.42	3.760%	$50.2406	$50.24	$50.25	$50.20
Purchase #2	$224.56	6.227%	$238.5434	$238.54	$238.55	$238.50
Purchase #3	$120.92	3.861%	$125.5887	$125.59	$125.60	$125.60
Purchase #4	$111.48	7.174%	$119.4776	$119.48	$119.50	$119.50
Purchase #5	$31.57	7.245%	$33.8572	$33.86	$33.85	$33.90
Purchase #6	$202.63	11.478%	$225.8879	$225.89	$225.90	$225.90
Purchase #7	$231.61	6.869%	$247.5193	$247.52	$247.50	$247.50
7 purchase totals =	$971.19		$1,041.1147	$1,041.12	$1,041.15	$1,041.10