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	$24.50	5.332%	$25.8063	$25.81	$25.80	$25.80
Purchase #2	$160.75	7.342%	$172.5523	$172.55	$172.55	$172.60
Purchase #3	$130.93	13.316%	$148.3646	$148.36	$148.35	$148.40
Purchase #4	$38.82	4.604%	$40.6073	$40.61	$40.60	$40.60
Purchase #5	$221.97	8.526%	$240.8952	$240.90	$240.90	$240.90
Purchase #6	$247.69	6.723%	$264.3422	$264.34	$264.35	$264.30
Purchase #7	$10.81	11.214%	$12.0222	$12.02	$12.00	$12.00
7 purchase totals =	$835.47		$904.5901	$904.59	$904.55	$904.60