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	$241.74	6.363%	$257.1219	$257.12	$257.10	$257.10
Purchase #2	$148.69	12.777%	$167.6881	$167.69	$167.70	$167.70
Purchase #3	$87.98	4.779%	$92.1846	$92.18	$92.20	$92.20
Purchase #4	$151.50	13.833%	$172.457	$172.46	$172.45	$172.50
Purchase #5	$132.76	4.755%	$139.0727	$139.07	$139.05	$139.10
Purchase #6	$137.87	5.799%	$145.8651	$145.87	$145.85	$145.90
Purchase #7	$81.27	6.442%	$86.5054	$86.51	$86.50	$86.50
7 purchase totals =	$981.81		$1,060.8948	$1,060.90	$1,060.85	$1,061.00