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	$205.30	9.737%	$225.2901	$225.29	$225.30	$225.30
Purchase #2	$30.83	8.763%	$33.5316	$33.53	$33.55	$33.50
Purchase #3	$73.71	6.500%	$78.5012	$78.50	$78.50	$78.50
Purchase #4	$89.91	3.648%	$93.1899	$93.19	$93.20	$93.20
Purchase #5	$110.27	5.561%	$116.4021	$116.40	$116.40	$116.40
Purchase #6	$76.35	6.205%	$81.0875	$81.09	$81.10	$81.10
Purchase #7	$83.39	9.863%	$91.6148	$91.61	$91.60	$91.60
7 purchase totals =	$669.76		$719.6172	$719.61	$719.65	$719.60