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	$214.56	13.164%	$242.8047	$242.80	$242.80	$242.80
Purchase #2	$190.55	5.303%	$200.6549	$200.65	$200.65	$200.70
Purchase #3	$42.74	6.577%	$45.551	$45.55	$45.55	$45.60
Purchase #4	$33.34	11.665%	$37.2291	$37.23	$37.25	$37.20
Purchase #5	$127.98	7.166%	$137.151	$137.15	$137.15	$137.20
Purchase #6	$42.39	12.118%	$47.5268	$47.53	$47.55	$47.50
Purchase #7	$112.51	12.487%	$126.5591	$126.56	$126.55	$126.60
7 purchase totals =	$764.07		$837.4766	$837.47	$837.50	$837.60