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	$32.76	13.851%	$37.2976	$37.30	$37.30	$37.30
Purchase #2	$74.88	11.312%	$83.3504	$83.35	$83.35	$83.40
Purchase #3	$89.54	13.676%	$101.7855	$101.79	$101.80	$101.80
Purchase #4	$85.69	6.830%	$91.5426	$91.54	$91.55	$91.50
Purchase #5	$234.34	10.647%	$259.2902	$259.29	$259.30	$259.30
Purchase #6	$217.69	11.806%	$243.3905	$243.39	$243.40	$243.40
Purchase #7	$61.25	7.442%	$65.8082	$65.81	$65.80	$65.80
7 purchase totals =	$796.15		$882.4650	$882.47	$882.50	$882.50