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	$208.73	4.284%	$217.672	$217.67	$217.65	$217.70
Purchase #2	$121.42	7.333%	$130.3237	$130.32	$130.30	$130.30
Purchase #3	$43.29	4.813%	$45.3735	$45.37	$45.35	$45.40
Purchase #4	$166.64	5.118%	$175.1686	$175.17	$175.15	$175.20
Purchase #5	$59.49	10.790%	$65.909	$65.91	$65.90	$65.90
Purchase #6	$129.27	12.184%	$145.0203	$145.02	$145.00	$145.00
Purchase #7	$118.78	7.176%	$127.3037	$127.30	$127.30	$127.30
7 purchase totals =	$847.62		$906.7708	$906.76	$906.65	$906.80