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	$153.94	9.359%	$168.3472	$168.35	$168.35	$168.30
Purchase #2	$238.91	13.134%	$270.2884	$270.29	$270.30	$270.30
Purchase #3	$247.63	11.702%	$276.6077	$276.61	$276.60	$276.60
Purchase #4	$178.53	6.599%	$190.3112	$190.31	$190.30	$190.30
Purchase #5	$49.48	6.479%	$52.6858	$52.69	$52.70	$52.70
Purchase #6	$13.80	6.761%	$14.733	$14.73	$14.75	$14.70
Purchase #7	$140.59	7.181%	$150.6858	$150.69	$150.70	$150.70
7 purchase totals =	$1,022.88		$1,123.6591	$1,123.67	$1,123.70	$1,123.60