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	$225.55	4.378%	$235.4246	$235.42	$235.40	$235.40
Purchase #2	$200.56	11.309%	$223.2413	$223.24	$223.25	$223.20
Purchase #3	$150.30	6.867%	$160.6211	$160.62	$160.60	$160.60
Purchase #4	$24.81	4.871%	$26.0185	$26.02	$26.00	$26.00
Purchase #5	$41.44	3.227%	$42.7773	$42.78	$42.80	$42.80
Purchase #6	$110.37	12.859%	$124.5625	$124.56	$124.55	$124.60
Purchase #7	$146.38	13.286%	$165.828	$165.83	$165.85	$165.80
7 purchase totals =	$899.41		$978.4733	$978.47	$978.45	$978.40