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	$107.30	8.456%	$116.3733	$116.37	$116.35	$116.40
Purchase #2	$132.31	6.817%	$141.3296	$141.33	$141.35	$141.30
Purchase #3	$79.59	5.129%	$83.6722	$83.67	$83.65	$83.70
Purchase #4	$53.25	8.513%	$57.7832	$57.78	$57.80	$57.80
Purchase #5	$103.81	8.733%	$112.8757	$112.88	$112.90	$112.90
Purchase #6	$31.29	3.833%	$32.4893	$32.49	$32.50	$32.50
Purchase #7	$240.78	9.500%	$263.6541	$263.65	$263.65	$263.70
7 purchase totals =	$748.33		$808.1774	$808.17	$808.20	$808.30