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 $209.96   10.507%   $232.0205   $232.02   $232.00   $232.00  
  Purchase #2 $217.49   6.753%   $232.1771   $232.18   $232.20   $232.20  
  Purchase #3 $75.75   6.432%   $80.6222   $80.62   $80.60   $80.60  
  Purchase #4 $136.78   3.283%   $141.2705   $141.27   $141.25   $141.30  
  Purchase #5 $19.46   13.646%   $22.1155   $22.12   $22.10   $22.10  
  Purchase #6 $207.40   3.496%   $214.6507   $214.65   $214.65   $214.70  
  Purchase #7 $179.47   6.688%   $191.473   $191.47   $191.45   $191.50  
  7 purchase totals = $1,046.31       $1,114.3295   $1,114.33   $1,114.25   $1,114.40