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 $114.84   8.823%   $124.9723   $124.97   $124.95   $125.00  
  Purchase #2 $237.71   12.515%   $267.4594   $267.46   $267.45   $267.50  
  Purchase #3 $19.27   8.118%   $20.8343   $20.83   $20.85   $20.80  
  Purchase #4 $184.71   11.439%   $205.839   $205.84   $205.85   $205.80  
  Purchase #5 $112.51   8.153%   $121.6829   $121.68   $121.70   $121.70  
  Purchase #6 $118.40   3.644%   $122.7145   $122.71   $122.70   $122.70  
  Purchase #7 $240.48   5.691%   $254.1657   $254.17   $254.15   $254.20  
  7 purchase totals = $1,027.92       $1,117.6681   $1,117.66   $1,117.65   $1,117.70