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 $41.67   10.652%   $46.1087   $46.11   $46.10   $46.10  
  Purchase #2 $240.55   11.295%   $267.7201   $267.72   $267.70   $267.70  
  Purchase #3 $122.84   7.574%   $132.1439   $132.14   $132.15   $132.10  
  Purchase #4 $206.95   12.677%   $233.1851   $233.19   $233.20   $233.20  
  Purchase #5 $205.65   13.494%   $233.4004   $233.40   $233.40   $233.40  
  Purchase #6 $214.28   6.179%   $227.5204   $227.52   $227.50   $227.50  
  Purchase #7 $209.60   9.557%   $229.6315   $229.63   $229.65   $229.60  
  7 purchase totals = $1,241.54       $1,369.7101   $1,369.71   $1,369.70   $1,369.60