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	$29.88	11.184%	$33.2218	$33.22	$33.20	$33.20
Purchase #2	$178.54	12.275%	$200.4558	$200.46	$200.45	$200.50
Purchase #3	$244.80	12.105%	$274.433	$274.43	$274.45	$274.40
Purchase #4	$42.66	3.448%	$44.1309	$44.13	$44.15	$44.10
Purchase #5	$240.58	5.663%	$254.204	$254.20	$254.20	$254.20
Purchase #6	$217.75	12.289%	$244.5093	$244.51	$244.50	$244.50
Purchase #7	$55.78	7.302%	$59.8531	$59.85	$59.85	$59.90
7 purchase totals =	$1,009.99		$1,110.8079	$1,110.80	$1,110.80	$1,110.80