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	$211.46	7.293%	$226.8818	$226.88	$226.90	$226.90
Purchase #2	$209.53	4.473%	$218.9023	$218.90	$218.90	$218.90
Purchase #3	$112.50	13.428%	$127.6065	$127.61	$127.60	$127.60
Purchase #4	$195.51	13.312%	$221.5363	$221.54	$221.55	$221.50
Purchase #5	$111.88	9.526%	$122.5377	$122.54	$122.55	$122.50
Purchase #6	$65.26	11.550%	$72.7975	$72.80	$72.80	$72.80
Purchase #7	$45.90	6.614%	$48.9358	$48.94	$48.95	$48.90
7 purchase totals =	$952.04		$1,039.1979	$1,039.21	$1,039.25	$1,039.10