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	$64.51	11.475%	$71.9125	$71.91	$71.90	$71.90
Purchase #2	$63.34	13.864%	$72.1215	$72.12	$72.10	$72.10
Purchase #3	$173.42	10.682%	$191.9447	$191.94	$191.95	$191.90
Purchase #4	$199.89	4.364%	$208.6132	$208.61	$208.60	$208.60
Purchase #5	$39.44	5.157%	$41.4739	$41.47	$41.45	$41.50
Purchase #6	$125.68	4.576%	$131.4311	$131.43	$131.45	$131.40
Purchase #7	$86.42	13.181%	$97.811	$97.81	$97.80	$97.80
7 purchase totals =	$752.70		$815.3079	$815.29	$815.25	$815.20