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	$85.79	9.795%	$94.1931	$94.19	$94.20	$94.20
Purchase #2	$228.34	5.353%	$240.563	$240.56	$240.55	$240.60
Purchase #3	$240.72	12.492%	$270.7907	$270.79	$270.80	$270.80
Purchase #4	$19.47	4.157%	$20.2794	$20.28	$20.30	$20.30
Purchase #5	$125.84	5.203%	$132.3875	$132.39	$132.40	$132.40
Purchase #6	$77.58	9.592%	$85.0215	$85.02	$85.00	$85.00
Purchase #7	$163.71	5.764%	$173.1462	$173.15	$173.15	$173.10
7 purchase totals =	$941.45		$1,016.3814	$1,016.38	$1,016.40	$1,016.40