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	$118.27	11.513%	$131.8864	$131.89	$131.90	$131.90
Purchase #2	$208.59	7.614%	$224.472	$224.47	$224.45	$224.50
Purchase #3	$98.84	4.434%	$103.2226	$103.22	$103.20	$103.20
Purchase #4	$142.66	6.462%	$151.8787	$151.88	$151.90	$151.90
Purchase #5	$67.82	13.345%	$76.8706	$76.87	$76.85	$76.90
Purchase #6	$124.39	9.466%	$136.1648	$136.16	$136.15	$136.20
Purchase #7	$175.78	7.510%	$188.9811	$188.98	$189.00	$189.00
7 purchase totals =	$936.35		$1,013.4762	$1,013.47	$1,013.45	$1,013.60