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	$238.86	7.496%	$256.7649	$256.76	$256.75	$256.80
Purchase #2	$36.27	8.449%	$39.3345	$39.33	$39.35	$39.30
Purchase #3	$186.72	10.737%	$206.7681	$206.77	$206.75	$206.80
Purchase #4	$73.67	5.321%	$77.59	$77.59	$77.60	$77.60
Purchase #5	$45.48	10.434%	$50.2254	$50.23	$50.25	$50.20
Purchase #6	$203.61	5.576%	$214.9633	$214.96	$214.95	$215.00
Purchase #7	$164.81	12.559%	$185.5085	$185.51	$185.50	$185.50
7 purchase totals =	$949.42		$1,031.1547	$1,031.15	$1,031.15	$1,031.20