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	$237.56	3.127%	$244.9885	$244.99	$245.00	$245.00
Purchase #2	$212.88	5.797%	$225.2207	$225.22	$225.20	$225.20
Purchase #3	$98.56	11.748%	$110.1388	$110.14	$110.15	$110.10
Purchase #4	$194.47	12.679%	$219.1269	$219.13	$219.15	$219.10
Purchase #5	$39.35	6.420%	$41.8763	$41.88	$41.90	$41.90
Purchase #6	$83.68	8.683%	$90.9459	$90.95	$90.95	$90.90
Purchase #7	$80.67	12.290%	$90.5843	$90.58	$90.60	$90.60
7 purchase totals =	$947.17		$1,022.8814	$1,022.89	$1,022.95	$1,022.80