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	$189.31	3.728%	$196.3675	$196.37	$196.35	$196.40
Purchase #2	$247.98	13.215%	$280.7506	$280.75	$280.75	$280.80
Purchase #3	$30.62	10.762%	$33.9153	$33.92	$33.90	$33.90
Purchase #4	$106.37	4.389%	$111.0386	$111.04	$111.05	$111.00
Purchase #5	$164.35	10.592%	$181.758	$181.76	$181.75	$181.80
Purchase #6	$56.25	12.672%	$63.378	$63.38	$63.40	$63.40
Purchase #7	$203.28	11.771%	$227.2081	$227.21	$227.20	$227.20
7 purchase totals =	$998.16		$1,094.4161	$1,094.43	$1,094.40	$1,094.50