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	$211.94	3.225%	$218.7751	$218.78	$218.80	$218.80
Purchase #2	$45.67	9.306%	$49.9201	$49.92	$49.90	$49.90
Purchase #3	$215.43	3.470%	$222.9054	$222.91	$222.90	$222.90
Purchase #4	$78.69	12.403%	$88.4499	$88.45	$88.45	$88.40
Purchase #5	$73.86	9.519%	$80.8907	$80.89	$80.90	$80.90
Purchase #6	$204.71	13.510%	$232.3663	$232.37	$232.35	$232.40
Purchase #7	$107.50	10.326%	$118.6005	$118.60	$118.60	$118.60
7 purchase totals =	$937.80		$1,011.9080	$1,011.92	$1,011.90	$1,011.90