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	$216.61	3.485%	$224.1589	$224.16	$224.15	$224.20
Purchase #2	$131.95	11.189%	$146.7139	$146.71	$146.70	$146.70
Purchase #3	$169.59	13.745%	$192.9001	$192.90	$192.90	$192.90
Purchase #4	$169.89	3.554%	$175.9279	$175.93	$175.95	$175.90
Purchase #5	$137.35	6.552%	$146.3492	$146.35	$146.35	$146.30
Purchase #6	$109.84	12.517%	$123.5887	$123.59	$123.60	$123.60
Purchase #7	$142.46	6.851%	$152.2199	$152.22	$152.20	$152.20
7 purchase totals =	$1,077.69		$1,161.8586	$1,161.86	$1,161.85	$1,161.80