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	$165.38	10.149%	$182.1644	$182.16	$182.15	$182.20
Purchase #2	$37.97	4.604%	$39.7181	$39.72	$39.70	$39.70
Purchase #3	$146.53	3.241%	$151.279	$151.28	$151.30	$151.30
Purchase #4	$113.82	3.203%	$117.4657	$117.47	$117.45	$117.50
Purchase #5	$216.77	11.863%	$242.4854	$242.49	$242.50	$242.50
Purchase #6	$137.39	13.815%	$156.3704	$156.37	$156.35	$156.40
Purchase #7	$97.43	7.399%	$104.6388	$104.64	$104.65	$104.60
7 purchase totals =	$915.29		$994.1218	$994.13	$994.10	$994.20