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	$215.27	5.128%	$226.309	$226.31	$226.30	$226.30
Purchase #2	$155.61	8.223%	$168.4058	$168.41	$168.40	$168.40
Purchase #3	$154.33	9.715%	$169.3232	$169.32	$169.30	$169.30
Purchase #4	$12.71	13.419%	$14.4156	$14.42	$14.40	$14.40
Purchase #5	$35.38	3.408%	$36.5858	$36.59	$36.60	$36.60
Purchase #6	$83.72	5.309%	$88.1647	$88.16	$88.15	$88.20
Purchase #7	$6.25	13.580%	$7.0988	$7.10	$7.10	$7.10
7 purchase totals =	$663.27		$710.3029	$710.31	$710.25	$710.30