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	$115.39	4.390%	$120.4556	$120.46	$120.45	$120.50
Purchase #2	$177.28	7.350%	$190.3101	$190.31	$190.30	$190.30
Purchase #3	$225.36	9.362%	$246.4582	$246.46	$246.45	$246.50
Purchase #4	$153.68	7.792%	$165.6547	$165.65	$165.65	$165.70
Purchase #5	$40.46	10.161%	$44.5711	$44.57	$44.55	$44.60
Purchase #6	$41.88	7.624%	$45.0729	$45.07	$45.05	$45.10
Purchase #7	$201.80	10.234%	$222.4522	$222.45	$222.45	$222.50
7 purchase totals =	$955.85		$1,034.9748	$1,034.97	$1,034.90	$1,035.20