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	$90.71	7.709%	$97.7028	$97.70	$97.70	$97.70
Purchase #2	$222.68	9.754%	$244.4002	$244.40	$244.40	$244.40
Purchase #3	$14.67	3.850%	$15.2348	$15.23	$15.25	$15.20
Purchase #4	$216.89	5.143%	$228.0447	$228.04	$228.05	$228.00
Purchase #5	$174.90	12.538%	$196.829	$196.83	$196.85	$196.80
Purchase #6	$188.48	6.208%	$200.1808	$200.18	$200.20	$200.20
Purchase #7	$200.40	13.566%	$227.5863	$227.59	$227.60	$227.60
7 purchase totals =	$1,108.73		$1,209.9786	$1,209.97	$1,210.05	$1,209.90