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 $105.68   8.168%   $114.3119   $114.31   $114.30   $114.30  
  Purchase #2 $187.88   6.372%   $199.8517   $199.85   $199.85   $199.90  
  Purchase #3 $238.52   5.165%   $250.8396   $250.84   $250.85   $250.80  
  Purchase #4 $10.63   11.119%   $11.8119   $11.81   $11.80   $11.80  
  Purchase #5 $146.58   9.374%   $160.3204   $160.32   $160.30   $160.30  
  Purchase #6 $72.65   8.771%   $79.0221   $79.02   $79.00   $79.00  
  Purchase #7 $224.35   5.605%   $236.9248   $236.92   $236.90   $236.90  
  7 purchase totals = $986.29       $1,053.0824   $1,053.07   $1,053.00   $1,053.00