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	$116.68	11.863%	$130.5217	$130.52	$130.50	$130.50
Purchase #2	$116.96	10.310%	$129.0186	$129.02	$129.00	$129.00
Purchase #3	$145.52	13.555%	$165.2452	$165.25	$165.25	$165.20
Purchase #4	$107.78	12.785%	$121.5597	$121.56	$121.55	$121.60
Purchase #5	$40.28	12.520%	$45.3231	$45.32	$45.30	$45.30
Purchase #6	$30.45	7.172%	$32.6339	$32.63	$32.65	$32.60
Purchase #7	$50.27	4.223%	$52.3929	$52.39	$52.40	$52.40
7 purchase totals =	$607.94		$676.6951	$676.69	$676.65	$676.60