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	$93.79	7.511%	$100.8346	$100.83	$100.85	$100.80
Purchase #2	$169.32	11.370%	$188.5717	$188.57	$188.55	$188.60
Purchase #3	$9.93	9.450%	$10.8684	$10.87	$10.85	$10.90
Purchase #4	$28.36	3.695%	$29.4079	$29.41	$29.40	$29.40
Purchase #5	$155.41	11.540%	$173.3443	$173.34	$173.35	$173.30
Purchase #6	$92.83	4.819%	$97.3035	$97.30	$97.30	$97.30
Purchase #7	$146.30	3.803%	$151.8638	$151.86	$151.85	$151.90
7 purchase totals =	$695.94		$752.1942	$752.18	$752.15	$752.20