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	$115.96	13.747%	$131.901	$131.90	$131.90	$131.90
Purchase #2	$199.38	5.845%	$211.0338	$211.03	$211.05	$211.00
Purchase #3	$102.54	3.177%	$105.7977	$105.80	$105.80	$105.80
Purchase #4	$172.81	10.300%	$190.6094	$190.61	$190.60	$190.60
Purchase #5	$83.72	10.334%	$92.3716	$92.37	$92.35	$92.40
Purchase #6	$63.83	11.499%	$71.1698	$71.17	$71.15	$71.20
Purchase #7	$142.76	5.516%	$150.6346	$150.63	$150.65	$150.60
7 purchase totals =	$881.00		$953.5179	$953.51	$953.50	$953.50