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 $244.90   7.768%   $263.9238   $263.92   $263.90   $263.90  
  Purchase #2 $86.95   9.563%   $95.265   $95.27   $95.25   $95.30  
  Purchase #3 $104.67   13.580%   $118.8842   $118.88   $118.90   $118.90  
  Purchase #4 $105.31   6.289%   $111.9329   $111.93   $111.95   $111.90  
  Purchase #5 $208.97   8.806%   $227.3719   $227.37   $227.35   $227.40  
  Purchase #6 $232.80   10.733%   $257.7864   $257.79   $257.80   $257.80  
  Purchase #7 $18.84   3.808%   $19.5574   $19.56   $19.55   $19.60  
  7 purchase totals = $1,002.44       $1,094.7216   $1,094.72   $1,094.70   $1,094.80