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	$132.57	3.535%	$137.2563	$137.26	$137.25	$137.30
Purchase #2	$188.60	11.337%	$209.9816	$209.98	$210.00	$210.00
Purchase #3	$165.90	8.639%	$180.2321	$180.23	$180.25	$180.20
Purchase #4	$133.81	13.560%	$151.9546	$151.95	$151.95	$152.00
Purchase #5	$231.36	10.218%	$255.0004	$255.00	$255.00	$255.00
Purchase #6	$139.74	8.148%	$151.126	$151.13	$151.15	$151.10
Purchase #7	$164.39	5.246%	$173.0139	$173.01	$173.00	$173.00
7 purchase totals =	$1,156.37		$1,258.5649	$1,258.56	$1,258.60	$1,258.60