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	$102.76	12.131%	$115.2258	$115.23	$115.25	$115.20
Purchase #2	$105.81	10.481%	$116.8999	$116.90	$116.90	$116.90
Purchase #3	$57.77	6.502%	$61.5262	$61.53	$61.55	$61.50
Purchase #4	$14.48	5.442%	$15.268	$15.27	$15.25	$15.30
Purchase #5	$37.67	7.385%	$40.4519	$40.45	$40.45	$40.50
Purchase #6	$59.70	6.815%	$63.7686	$63.77	$63.75	$63.80
Purchase #7	$57.98	5.763%	$61.3214	$61.32	$61.30	$61.30
7 purchase totals =	$436.17		$474.4618	$474.47	$474.45	$474.50