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	$208.26	5.128%	$218.9396	$218.94	$218.95	$218.90
Purchase #2	$175.30	13.860%	$199.5966	$199.60	$199.60	$199.60
Purchase #3	$156.84	3.631%	$162.5349	$162.53	$162.55	$162.50
Purchase #4	$206.65	5.803%	$218.6419	$218.64	$218.65	$218.60
Purchase #5	$155.74	10.661%	$172.3434	$172.34	$172.35	$172.30
Purchase #6	$33.96	10.759%	$37.6138	$37.61	$37.60	$37.60
Purchase #7	$232.67	12.824%	$262.5076	$262.51	$262.50	$262.50
7 purchase totals =	$1,169.42		$1,272.1778	$1,272.17	$1,272.20	$1,272.00