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	$99.33	4.523%	$103.8227	$103.82	$103.80	$103.80
Purchase #2	$170.90	10.311%	$188.5215	$188.52	$188.50	$188.50
Purchase #3	$233.38	5.228%	$245.5811	$245.58	$245.60	$245.60
Purchase #4	$203.90	11.733%	$227.8236	$227.82	$227.80	$227.80
Purchase #5	$217.30	9.619%	$238.2021	$238.20	$238.20	$238.20
Purchase #6	$9.66	6.170%	$10.256	$10.26	$10.25	$10.30
Purchase #7	$137.55	10.343%	$151.7768	$151.78	$151.80	$151.80
7 purchase totals =	$1,072.02		$1,165.9838	$1,165.98	$1,165.95	$1,166.00