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	$42.97	7.316%	$46.1137	$46.11	$46.10	$46.10
Purchase #2	$198.62	11.562%	$221.5844	$221.58	$221.60	$221.60
Purchase #3	$190.26	11.653%	$212.431	$212.43	$212.45	$212.40
Purchase #4	$30.49	4.338%	$31.8127	$31.81	$31.80	$31.80
Purchase #5	$65.80	6.622%	$70.1573	$70.16	$70.15	$70.20
Purchase #6	$78.92	13.492%	$89.5679	$89.57	$89.55	$89.60
Purchase #7	$38.30	3.730%	$39.7286	$39.73	$39.75	$39.70
7 purchase totals =	$645.36		$711.3956	$711.39	$711.40	$711.40