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	$147.28	13.463%	$167.1083	$167.11	$167.10	$167.10
Purchase #2	$118.45	10.205%	$130.5378	$130.54	$130.55	$130.50
Purchase #3	$124.54	5.103%	$130.8953	$130.90	$130.90	$130.90
Purchase #4	$223.86	8.740%	$243.4254	$243.43	$243.45	$243.40
Purchase #5	$132.61	4.752%	$138.9116	$138.91	$138.90	$138.90
Purchase #6	$198.89	8.354%	$215.5053	$215.51	$215.50	$215.50
Purchase #7	$20.87	5.729%	$22.0656	$22.07	$22.05	$22.10
7 purchase totals =	$966.50		$1,048.4493	$1,048.47	$1,048.45	$1,048.40