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	$120.55	13.452%	$136.7664	$136.77	$136.75	$136.80
Purchase #2	$196.38	3.133%	$202.5326	$202.53	$202.55	$202.50
Purchase #3	$118.65	3.744%	$123.0923	$123.09	$123.10	$123.10
Purchase #4	$86.38	4.103%	$89.9242	$89.92	$89.90	$89.90
Purchase #5	$41.60	6.666%	$44.3731	$44.37	$44.35	$44.40
Purchase #6	$214.51	3.309%	$221.6081	$221.61	$221.60	$221.60
Purchase #7	$53.80	5.678%	$56.8548	$56.85	$56.85	$56.90
7 purchase totals =	$831.87		$875.1515	$875.14	$875.10	$875.20