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	$108.65	13.387%	$123.195	$123.20	$123.20	$123.20
Purchase #2	$25.38	7.367%	$27.2497	$27.25	$27.25	$27.20
Purchase #3	$115.87	9.500%	$126.8777	$126.88	$126.90	$126.90
Purchase #4	$221.86	11.473%	$247.314	$247.31	$247.30	$247.30
Purchase #5	$181.92	9.574%	$199.337	$199.34	$199.35	$199.30
Purchase #6	$101.90	9.526%	$111.607	$111.61	$111.60	$111.60
Purchase #7	$135.74	4.514%	$141.8673	$141.87	$141.85	$141.90
7 purchase totals =	$891.32		$977.4477	$977.46	$977.45	$977.40