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	$104.53	6.345%	$111.1624	$111.16	$111.15	$111.20
Purchase #2	$72.78	6.635%	$77.609	$77.61	$77.60	$77.60
Purchase #3	$39.58	9.634%	$43.3931	$43.39	$43.40	$43.40
Purchase #4	$43.83	12.479%	$49.2995	$49.30	$49.30	$49.30
Purchase #5	$53.89	3.569%	$55.8133	$55.81	$55.80	$55.80
Purchase #6	$199.73	6.587%	$212.8862	$212.89	$212.90	$212.90
Purchase #7	$81.51	7.279%	$87.4431	$87.44	$87.45	$87.40
7 purchase totals =	$595.85		$637.6066	$637.60	$637.60	$637.60