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	$216.41	11.150%	$240.5397	$240.54	$240.55	$240.50
Purchase #2	$222.27	6.406%	$236.5086	$236.51	$236.50	$236.50
Purchase #3	$131.59	8.283%	$142.4896	$142.49	$142.50	$142.50
Purchase #4	$149.47	8.186%	$161.7056	$161.71	$161.70	$161.70
Purchase #5	$20.39	7.385%	$21.8958	$21.90	$21.90	$21.90
Purchase #6	$31.78	11.412%	$35.4067	$35.41	$35.40	$35.40
Purchase #7	$165.82	8.189%	$179.399	$179.40	$179.40	$179.40
7 purchase totals =	$937.73		$1,017.9450	$1,017.96	$1,017.95	$1,017.90