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	$194.68	12.817%	$219.6321	$219.63	$219.65	$219.60
Purchase #2	$64.80	13.836%	$73.7657	$73.77	$73.75	$73.80
Purchase #3	$90.82	10.673%	$100.5132	$100.51	$100.50	$100.50
Purchase #4	$100.53	5.153%	$105.7103	$105.71	$105.70	$105.70
Purchase #5	$109.31	9.446%	$119.6354	$119.64	$119.65	$119.60
Purchase #6	$62.95	13.384%	$71.3752	$71.38	$71.40	$71.40
Purchase #7	$56.30	10.496%	$62.2092	$62.21	$62.20	$62.20
7 purchase totals =	$679.39		$752.8411	$752.85	$752.85	$752.80