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 $116.76   8.724%   $126.9461   $126.95   $126.95   $126.90  
  Purchase #2 $203.81   7.306%   $218.7004   $218.70   $218.70   $218.70  
  Purchase #3 $229.78   8.496%   $249.3021   $249.30   $249.30   $249.30  
  Purchase #4 $38.43   8.676%   $41.7642   $41.76   $41.75   $41.80  
  Purchase #5 $25.73   8.631%   $27.9508   $27.95   $27.95   $28.00  
  Purchase #6 $197.38   8.413%   $213.9856   $213.99   $214.00   $214.00  
  Purchase #7 $237.86   6.644%   $253.6634   $253.66   $253.65   $253.70  
  7 purchase totals = $1,049.75       $1,132.3126   $1,132.31   $1,132.30   $1,132.40