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	$55.59	13.440%	$63.0613	$63.06	$63.05	$63.10
Purchase #2	$143.47	5.320%	$151.1026	$151.10	$151.10	$151.10
Purchase #3	$149.59	12.609%	$168.4518	$168.45	$168.45	$168.50
Purchase #4	$78.81	7.421%	$84.6585	$84.66	$84.65	$84.70
Purchase #5	$233.44	3.633%	$241.9209	$241.92	$241.90	$241.90
Purchase #6	$92.98	11.258%	$103.4477	$103.45	$103.45	$103.40
Purchase #7	$76.25	8.213%	$82.5124	$82.51	$82.50	$82.50
7 purchase totals =	$830.13		$895.1552	$895.15	$895.10	$895.20