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 $173.25   13.712%   $197.006   $197.01   $197.00   $197.00  
  Purchase #2 $76.62   6.359%   $81.4923   $81.49   $81.50   $81.50  
  Purchase #3 $53.35   7.197%   $57.1896   $57.19   $57.20   $57.20  
  Purchase #4 $225.45   3.757%   $233.9202   $233.92   $233.90   $233.90  
  Purchase #5 $250.65   5.285%   $263.8969   $263.90   $263.90   $263.90  
  Purchase #6 $84.39   11.146%   $93.7961   $93.80   $93.80   $93.80  
  Purchase #7 $131.51   9.684%   $144.2454   $144.25   $144.25   $144.20  
  7 purchase totals = $995.22       $1,071.5465   $1,071.56   $1,071.55   $1,071.50