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	$34.63	7.105%	$37.0905	$37.09	$37.10	$37.10
Purchase #2	$133.61	11.615%	$149.1288	$149.13	$149.15	$149.10
Purchase #3	$35.90	3.874%	$37.2908	$37.29	$37.30	$37.30
Purchase #4	$78.62	8.224%	$85.0857	$85.09	$85.10	$85.10
Purchase #5	$64.97	4.258%	$67.7364	$67.74	$67.75	$67.70
Purchase #6	$246.35	10.166%	$271.3939	$271.39	$271.40	$271.40
Purchase #7	$221.31	12.137%	$248.1704	$248.17	$248.15	$248.20
7 purchase totals =	$815.39		$895.8965	$895.90	$895.95	$895.90