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	$195.61	13.562%	$222.1386	$222.14	$222.15	$222.10
Purchase #2	$110.71	11.540%	$123.4859	$123.49	$123.50	$123.50
Purchase #3	$209.96	11.217%	$233.5112	$233.51	$233.50	$233.50
Purchase #4	$151.85	8.522%	$164.7907	$164.79	$164.80	$164.80
Purchase #5	$20.38	11.561%	$22.7361	$22.74	$22.75	$22.70
Purchase #6	$13.84	12.779%	$15.6086	$15.61	$15.60	$15.60
Purchase #7	$108.97	11.293%	$121.276	$121.28	$121.30	$121.30
7 purchase totals =	$811.32		$903.5471	$903.56	$903.60	$903.50