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	$36.27	3.134%	$37.4067	$37.41	$37.40	$37.40
Purchase #2	$169.56	6.420%	$180.4458	$180.45	$180.45	$180.40
Purchase #3	$232.42	4.269%	$242.342	$242.34	$242.35	$242.30
Purchase #4	$211.63	4.560%	$221.2803	$221.28	$221.30	$221.30
Purchase #5	$63.71	5.520%	$67.2268	$67.23	$67.25	$67.20
Purchase #6	$111.96	5.624%	$118.2566	$118.26	$118.25	$118.30
Purchase #7	$32.83	13.663%	$37.3156	$37.32	$37.30	$37.30
7 purchase totals =	$858.38		$904.2738	$904.29	$904.30	$904.20