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 $212.25   11.383%   $236.4104   $236.41   $236.40   $236.40  
  Purchase #2 $212.32   13.334%   $240.6307   $240.63   $240.65   $240.60  
  Purchase #3 $21.50   10.120%   $23.6758   $23.68   $23.70   $23.70  
  Purchase #4 $213.53   11.360%   $237.787   $237.79   $237.80   $237.80  
  Purchase #5 $157.80   11.871%   $176.5324   $176.53   $176.55   $176.50  
  Purchase #6 $206.95   9.503%   $226.6165   $226.62   $226.60   $226.60  
  Purchase #7 $55.64   12.568%   $62.6328   $62.63   $62.65   $62.60  
  7 purchase totals = $1,079.99       $1,204.2856   $1,204.29   $1,204.35   $1,204.20