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 $219.47   5.727%   $232.039   $232.04   $232.05   $232.00  
  Purchase #2 $36.31   3.755%   $37.6734   $37.67   $37.65   $37.70  
  Purchase #3 $52.64   4.478%   $54.9972   $55.00   $55.00   $55.00  
  Purchase #4 $101.86   5.669%   $107.6344   $107.63   $107.65   $107.60  
  Purchase #5 $227.56   4.334%   $237.4225   $237.42   $237.40   $237.40  
  Purchase #6 $179.64   12.333%   $201.795   $201.80   $201.80   $201.80  
  Purchase #7 $247.95   8.842%   $269.8737   $269.87   $269.85   $269.90  
  7 purchase totals = $1,065.43       $1,141.4352   $1,141.43   $1,141.40   $1,141.40