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	$41.95	10.361%	$46.2964	$46.30	$46.30	$46.30
Purchase #2	$96.44	10.665%	$106.7253	$106.73	$106.75	$106.70
Purchase #3	$209.62	4.172%	$218.3653	$218.37	$218.35	$218.40
Purchase #4	$11.81	3.540%	$12.2281	$12.23	$12.25	$12.20
Purchase #5	$96.63	8.260%	$104.6116	$104.61	$104.60	$104.60
Purchase #6	$37.83	5.141%	$39.7748	$39.77	$39.75	$39.80
Purchase #7	$113.55	8.861%	$123.6117	$123.61	$123.60	$123.60
7 purchase totals =	$607.83		$651.6132	$651.62	$651.60	$651.60