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	$133.72	4.208%	$139.3469	$139.35	$139.35	$139.30
Purchase #2	$236.60	4.719%	$247.7652	$247.77	$247.75	$247.80
Purchase #3	$166.66	10.739%	$184.5576	$184.56	$184.55	$184.60
Purchase #4	$49.92	5.238%	$52.5348	$52.53	$52.55	$52.50
Purchase #5	$157.91	13.590%	$179.37	$179.37	$179.35	$179.40
Purchase #6	$182.47	9.379%	$199.5839	$199.58	$199.60	$199.60
Purchase #7	$35.51	13.593%	$40.3369	$40.34	$40.35	$40.30
7 purchase totals =	$962.79		$1,043.4953	$1,043.50	$1,043.50	$1,043.50