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	$117.66	7.399%	$126.3657	$126.37	$126.35	$126.40
Purchase #2	$6.40	13.296%	$7.2509	$7.25	$7.25	$7.30
Purchase #3	$24.80	13.536%	$28.1569	$28.16	$28.15	$28.20
Purchase #4	$59.33	12.770%	$66.9064	$66.91	$66.90	$66.90
Purchase #5	$55.41	7.119%	$59.3546	$59.35	$59.35	$59.40
Purchase #6	$176.33	7.686%	$189.8827	$189.88	$189.90	$189.90
Purchase #7	$223.73	13.121%	$253.0856	$253.09	$253.10	$253.10
7 purchase totals =	$663.66		$731.0028	$731.01	$731.00	$731.20