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 $183.80   7.541%   $197.6604   $197.66   $197.65   $197.70  
  Purchase #2 $119.47   13.460%   $135.5507   $135.55   $135.55   $135.60  
  Purchase #3 $161.99   9.328%   $177.1004   $177.10   $177.10   $177.10  
  Purchase #4 $205.59   10.588%   $227.3579   $227.36   $227.35   $227.40  
  Purchase #5 $127.49   4.153%   $132.7847   $132.78   $132.80   $132.80  
  Purchase #6 $48.81   4.447%   $50.9806   $50.98   $51.00   $51.00  
  Purchase #7 $108.55   13.192%   $122.8699   $122.87   $122.85   $122.90  
  7 purchase totals = $955.70       $1,044.3046   $1,044.30   $1,044.30   $1,044.50