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	$230.95	12.483%	$259.7795	$259.78	$259.80	$259.80
Purchase #2	$148.87	7.204%	$159.5946	$159.59	$159.60	$159.60
Purchase #3	$132.58	3.625%	$137.386	$137.39	$137.40	$137.40
Purchase #4	$140.51	11.642%	$156.8682	$156.87	$156.85	$156.90
Purchase #5	$55.42	13.431%	$62.8635	$62.86	$62.85	$62.90
Purchase #6	$177.30	11.590%	$197.8491	$197.85	$197.85	$197.80
Purchase #7	$137.37	3.535%	$142.226	$142.23	$142.25	$142.20
7 purchase totals =	$1,023.00		$1,116.5669	$1,116.57	$1,116.60	$1,116.60