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	$209.59	8.856%	$228.1513	$228.15	$228.15	$228.20
Purchase #2	$122.40	12.392%	$137.5678	$137.57	$137.55	$137.60
Purchase #3	$48.99	9.223%	$53.5083	$53.51	$53.50	$53.50
Purchase #4	$239.50	7.103%	$256.5117	$256.51	$256.50	$256.50
Purchase #5	$170.47	12.566%	$191.8913	$191.89	$191.90	$191.90
Purchase #6	$153.66	10.835%	$170.3091	$170.31	$170.30	$170.30
Purchase #7	$121.38	13.229%	$137.4374	$137.44	$137.45	$137.40
7 purchase totals =	$1,065.99		$1,175.3769	$1,175.38	$1,175.35	$1,175.40