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	$104.30	13.691%	$118.5797	$118.58	$118.60	$118.60
Purchase #2	$144.39	5.228%	$151.9387	$151.94	$151.95	$151.90
Purchase #3	$215.76	12.574%	$242.8897	$242.89	$242.90	$242.90
Purchase #4	$118.95	7.780%	$128.2043	$128.20	$128.20	$128.20
Purchase #5	$166.29	9.324%	$181.7949	$181.79	$181.80	$181.80
Purchase #6	$8.76	3.579%	$9.0735	$9.07	$9.05	$9.10
Purchase #7	$213.27	7.588%	$229.4529	$229.45	$229.45	$229.50
7 purchase totals =	$971.72		$1,061.9337	$1,061.92	$1,061.95	$1,062.00