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	$192.47	13.400%	$218.261	$218.26	$218.25	$218.30
Purchase #2	$92.30	8.660%	$100.2932	$100.29	$100.30	$100.30
Purchase #3	$244.67	5.587%	$258.3397	$258.34	$258.35	$258.30
Purchase #4	$247.85	3.213%	$255.8134	$255.81	$255.80	$255.80
Purchase #5	$60.41	7.317%	$64.8302	$64.83	$64.85	$64.80
Purchase #6	$94.66	13.732%	$107.6587	$107.66	$107.65	$107.70
Purchase #7	$38.29	12.117%	$42.9296	$42.93	$42.95	$42.90
7 purchase totals =	$970.65		$1,048.1258	$1,048.12	$1,048.15	$1,048.10