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 $240.63   9.303%   $263.0158   $263.02   $263.00   $263.00  
  Purchase #2 $208.98   13.793%   $237.8046   $237.80   $237.80   $237.80  
  Purchase #3 $36.54   10.540%   $40.3913   $40.39   $40.40   $40.40  
  Purchase #4 $153.39   13.123%   $173.5194   $173.52   $173.50   $173.50  
  Purchase #5 $67.90   13.596%   $77.1317   $77.13   $77.15   $77.10  
  Purchase #6 $169.26   11.286%   $188.3627   $188.36   $188.35   $188.40  
  Purchase #7 $39.58   11.698%   $44.2101   $44.21   $44.20   $44.20  
  7 purchase totals = $916.28       $1,024.4356   $1,024.43   $1,024.40   $1,024.40