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	$63.96	12.488%	$71.9473	$71.95	$71.95	$71.90
Purchase #2	$131.78	13.104%	$149.0485	$149.05	$149.05	$149.00
Purchase #3	$111.94	10.465%	$123.6545	$123.65	$123.65	$123.70
Purchase #4	$228.77	13.375%	$259.368	$259.37	$259.35	$259.40
Purchase #5	$85.38	8.330%	$92.4922	$92.49	$92.50	$92.50
Purchase #6	$143.45	6.564%	$152.8661	$152.87	$152.85	$152.90
Purchase #7	$139.97	9.574%	$153.3707	$153.37	$153.35	$153.40
7 purchase totals =	$905.25		$1,002.7473	$1,002.75	$1,002.70	$1,002.80