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	$36.31	7.254%	$38.9439	$38.94	$38.95	$38.90
Purchase #2	$93.73	7.386%	$100.6529	$100.65	$100.65	$100.70
Purchase #3	$181.64	3.180%	$187.4162	$187.42	$187.40	$187.40
Purchase #4	$241.66	12.233%	$271.2223	$271.22	$271.20	$271.20
Purchase #5	$30.54	6.270%	$32.4549	$32.45	$32.45	$32.50
Purchase #6	$45.77	9.583%	$50.1561	$50.16	$50.15	$50.20
Purchase #7	$20.70	5.544%	$21.8476	$21.85	$21.85	$21.80
7 purchase totals =	$650.35		$702.6939	$702.69	$702.65	$702.70