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	$143.69	13.531%	$163.1327	$163.13	$163.15	$163.10
Purchase #2	$200.61	13.229%	$227.1487	$227.15	$227.15	$227.10
Purchase #3	$166.65	4.197%	$173.6443	$173.64	$173.65	$173.60
Purchase #4	$12.44	8.612%	$13.5113	$13.51	$13.50	$13.50
Purchase #5	$35.30	6.336%	$37.5366	$37.54	$37.55	$37.50
Purchase #6	$181.37	4.860%	$190.1846	$190.18	$190.20	$190.20
Purchase #7	$220.47	13.799%	$250.8927	$250.89	$250.90	$250.90
7 purchase totals =	$960.53		$1,056.0509	$1,056.04	$1,056.10	$1,055.90