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	$243.65	8.257%	$263.7682	$263.77	$263.75	$263.80
Purchase #2	$160.58	3.181%	$165.688	$165.69	$165.70	$165.70
Purchase #3	$130.42	10.238%	$143.7724	$143.77	$143.75	$143.80
Purchase #4	$239.61	6.734%	$255.7453	$255.75	$255.75	$255.70
Purchase #5	$38.83	4.628%	$40.6271	$40.63	$40.65	$40.60
Purchase #6	$147.56	8.359%	$159.8945	$159.89	$159.90	$159.90
Purchase #7	$214.59	3.171%	$221.3946	$221.39	$221.40	$221.40
7 purchase totals =	$1,175.24		$1,250.8901	$1,250.89	$1,250.90	$1,250.90