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	$116.52	12.830%	$131.4695	$131.47	$131.45	$131.50
Purchase #2	$90.72	5.115%	$95.3603	$95.36	$95.35	$95.40
Purchase #3	$241.27	13.792%	$274.546	$274.55	$274.55	$274.50
Purchase #4	$214.59	7.406%	$230.4825	$230.48	$230.50	$230.50
Purchase #5	$175.36	7.299%	$188.1595	$188.16	$188.15	$188.20
Purchase #6	$55.56	4.103%	$57.8396	$57.84	$57.85	$57.80
Purchase #7	$141.73	4.737%	$148.4438	$148.44	$148.45	$148.40
7 purchase totals =	$1,035.75		$1,126.3012	$1,126.30	$1,126.30	$1,126.30