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	$192.92	13.316%	$218.6092	$218.61	$218.60	$218.60
Purchase #2	$56.63	8.516%	$61.4526	$61.45	$61.45	$61.50
Purchase #3	$9.52	10.542%	$10.5236	$10.52	$10.50	$10.50
Purchase #4	$151.49	13.219%	$171.5155	$171.52	$171.50	$171.50
Purchase #5	$153.33	12.307%	$172.2003	$172.20	$172.20	$172.20
Purchase #6	$218.82	13.102%	$247.4898	$247.49	$247.50	$247.50
Purchase #7	$222.25	11.544%	$247.9065	$247.91	$247.90	$247.90
7 purchase totals =	$1,004.96		$1,129.6975	$1,129.70	$1,129.65	$1,129.70