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	$213.66	5.375%	$225.1442	$225.14	$225.15	$225.10
Purchase #2	$132.60	9.656%	$145.4039	$145.40	$145.40	$145.40
Purchase #3	$31.88	3.676%	$33.0519	$33.05	$33.05	$33.10
Purchase #4	$162.61	13.787%	$185.029	$185.03	$185.05	$185.00
Purchase #5	$172.68	5.601%	$182.3518	$182.35	$182.35	$182.40
Purchase #6	$207.50	8.866%	$225.897	$225.90	$225.90	$225.90
Purchase #7	$94.54	5.266%	$99.5185	$99.52	$99.50	$99.50
7 purchase totals =	$1,015.47		$1,096.3963	$1,096.39	$1,096.40	$1,096.40