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	$67.32	6.429%	$71.648	$71.65	$71.65	$71.60
Purchase #2	$201.26	10.694%	$222.7827	$222.78	$222.80	$222.80
Purchase #3	$196.46	6.326%	$208.8881	$208.89	$208.90	$208.90
Purchase #4	$192.25	11.741%	$214.8221	$214.82	$214.80	$214.80
Purchase #5	$240.83	6.529%	$256.5538	$256.55	$256.55	$256.60
Purchase #6	$118.36	10.366%	$130.6292	$130.63	$130.65	$130.60
Purchase #7	$141.86	4.764%	$148.6182	$148.62	$148.60	$148.60
7 purchase totals =	$1,158.34		$1,253.9421	$1,253.94	$1,253.95	$1,253.90