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	$29.87	8.673%	$32.4606	$32.46	$32.45	$32.50
Purchase #2	$218.78	13.295%	$247.8668	$247.87	$247.85	$247.90
Purchase #3	$117.76	11.116%	$130.8502	$130.85	$130.85	$130.90
Purchase #4	$14.77	7.602%	$15.8928	$15.89	$15.90	$15.90
Purchase #5	$58.79	11.863%	$65.7643	$65.76	$65.75	$65.80
Purchase #6	$12.31	12.595%	$13.8604	$13.86	$13.85	$13.90
Purchase #7	$231.28	8.238%	$250.3328	$250.33	$250.35	$250.30
7 purchase totals =	$683.56		$757.0279	$757.02	$757.00	$757.20