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	$93.97	12.184%	$105.4193	$105.42	$105.40	$105.40
Purchase #2	$170.54	8.722%	$185.4145	$185.41	$185.40	$185.40
Purchase #3	$25.45	6.726%	$27.1618	$27.16	$27.15	$27.20
Purchase #4	$153.44	9.634%	$168.2224	$168.22	$168.20	$168.20
Purchase #5	$117.26	8.264%	$126.9504	$126.95	$126.95	$127.00
Purchase #6	$54.40	9.635%	$59.6414	$59.64	$59.65	$59.60
Purchase #7	$83.46	10.578%	$92.2884	$92.29	$92.30	$92.30
7 purchase totals =	$698.52		$765.0982	$765.09	$765.05	$765.10