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	$228.65	8.193%	$247.3833	$247.38	$247.40	$247.40
Purchase #2	$50.71	11.402%	$56.492	$56.49	$56.50	$56.50
Purchase #3	$203.89	11.415%	$227.164	$227.16	$227.15	$227.20
Purchase #4	$85.51	10.188%	$94.2218	$94.22	$94.20	$94.20
Purchase #5	$56.56	12.445%	$63.5989	$63.60	$63.60	$63.60
Purchase #6	$53.26	11.530%	$59.4009	$59.40	$59.40	$59.40
Purchase #7	$157.77	7.439%	$169.5065	$169.51	$169.50	$169.50
7 purchase totals =	$836.35		$917.7674	$917.76	$917.75	$917.80