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 $58.80   10.541%   $64.9981   $65.00   $65.00   $65.00  
  Purchase #2 $248.57   11.170%   $276.3353   $276.34   $276.35   $276.30  
  Purchase #3 $143.82   12.550%   $161.8694   $161.87   $161.85   $161.90  
  Purchase #4 $93.62   11.575%   $104.4565   $104.46   $104.45   $104.50  
  Purchase #5 $125.78   10.367%   $138.8196   $138.82   $138.80   $138.80  
  Purchase #6 $114.91   8.488%   $124.6636   $124.66   $124.65   $124.70  
  Purchase #7 $137.27   12.481%   $154.4027   $154.40   $154.40   $154.40  
  7 purchase totals = $922.77       $1,025.5452   $1,025.55   $1,025.50   $1,025.60