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 $179.96   8.146%   $194.6195   $194.62   $194.60   $194.60  
  Purchase #2 $236.35   10.570%   $261.3322   $261.33   $261.35   $261.30  
  Purchase #3 $174.27   8.335%   $188.7954   $188.80   $188.80   $188.80  
  Purchase #4 $10.69   7.145%   $11.4538   $11.45   $11.45   $11.50  
  Purchase #5 $147.79   13.785%   $168.1629   $168.16   $168.15   $168.20  
  Purchase #6 $191.79   13.800%   $218.257   $218.26   $218.25   $218.30  
  Purchase #7 $15.63   10.852%   $17.3262   $17.33   $17.35   $17.30  
  7 purchase totals = $956.48       $1,059.9470   $1,059.95   $1,059.95   $1,060.00