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	$77.89	9.694%	$85.4407	$85.44	$85.45	$85.40
Purchase #2	$165.62	10.243%	$182.5845	$182.58	$182.60	$182.60
Purchase #3	$49.74	13.123%	$56.2674	$56.27	$56.25	$56.30
Purchase #4	$223.63	13.375%	$253.5405	$253.54	$253.55	$253.50
Purchase #5	$146.51	11.224%	$162.9543	$162.95	$162.95	$163.00
Purchase #6	$124.48	9.735%	$136.5981	$136.60	$136.60	$136.60
Purchase #7	$205.70	9.799%	$225.8565	$225.86	$225.85	$225.90
7 purchase totals =	$993.57		$1,103.2420	$1,103.24	$1,103.25	$1,103.30