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	$208.64	8.237%	$225.8257	$225.83	$225.85	$225.80
Purchase #2	$134.41	10.271%	$148.2153	$148.22	$148.20	$148.20
Purchase #3	$234.30	5.551%	$247.306	$247.31	$247.30	$247.30
Purchase #4	$83.28	3.504%	$86.1981	$86.20	$86.20	$86.20
Purchase #5	$161.48	6.709%	$172.3137	$172.31	$172.30	$172.30
Purchase #6	$135.69	12.307%	$152.3894	$152.39	$152.40	$152.40
Purchase #7	$81.67	10.762%	$90.4593	$90.46	$90.45	$90.50
7 purchase totals =	$1,039.47		$1,122.7075	$1,122.72	$1,122.70	$1,122.70