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	$201.72	11.684%	$225.289	$225.29	$225.30	$225.30
Purchase #2	$17.61	12.800%	$19.8641	$19.86	$19.85	$19.90
Purchase #3	$109.45	8.791%	$119.0717	$119.07	$119.05	$119.10
Purchase #4	$33.96	4.599%	$35.5218	$35.52	$35.50	$35.50
Purchase #5	$136.73	7.487%	$146.967	$146.97	$146.95	$147.00
Purchase #6	$121.31	4.771%	$127.0977	$127.10	$127.10	$127.10
Purchase #7	$42.54	4.223%	$44.3365	$44.34	$44.35	$44.30
7 purchase totals =	$663.32		$718.1478	$718.15	$718.10	$718.20