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	$40.74	12.354%	$45.773	$45.77	$45.75	$45.80
Purchase #2	$23.68	11.748%	$26.4619	$26.46	$26.45	$26.50
Purchase #3	$78.72	8.367%	$85.3065	$85.31	$85.30	$85.30
Purchase #4	$155.97	10.453%	$172.2735	$172.27	$172.25	$172.30
Purchase #5	$31.73	8.644%	$34.4727	$34.47	$34.45	$34.50
Purchase #6	$94.77	5.494%	$99.9767	$99.98	$100.00	$100.00
Purchase #7	$195.69	11.419%	$218.0358	$218.04	$218.05	$218.00
7 purchase totals =	$621.30		$682.3001	$682.30	$682.25	$682.40