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	$64.94	11.683%	$72.5269	$72.53	$72.55	$72.50
Purchase #2	$102.64	4.155%	$106.9047	$106.90	$106.90	$106.90
Purchase #3	$198.90	12.385%	$223.5338	$223.53	$223.55	$223.50
Purchase #4	$25.95	11.847%	$29.0243	$29.02	$29.00	$29.00
Purchase #5	$185.29	5.703%	$195.8571	$195.86	$195.85	$195.90
Purchase #6	$112.64	5.787%	$119.1585	$119.16	$119.15	$119.20
Purchase #7	$177.79	12.736%	$200.4333	$200.43	$200.45	$200.40
7 purchase totals =	$868.15		$947.4386	$947.43	$947.45	$947.40