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	$234.56	13.289%	$265.7307	$265.73	$265.75	$265.70
Purchase #2	$201.39	10.421%	$222.3769	$222.38	$222.40	$222.40
Purchase #3	$13.73	7.321%	$14.7352	$14.74	$14.75	$14.70
Purchase #4	$167.66	13.571%	$190.4131	$190.41	$190.40	$190.40
Purchase #5	$146.46	11.862%	$163.8331	$163.83	$163.85	$163.80
Purchase #6	$232.27	10.189%	$255.936	$255.94	$255.95	$255.90
Purchase #7	$17.76	4.160%	$18.4988	$18.50	$18.50	$18.50
7 purchase totals =	$1,013.83		$1,131.5238	$1,131.53	$1,131.60	$1,131.40