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 $239.35   12.577%   $269.453   $269.45   $269.45   $269.50  
  Purchase #2 $201.58   5.317%   $212.298   $212.30   $212.30   $212.30  
  Purchase #3 $69.71   8.290%   $75.489   $75.49   $75.50   $75.50  
  Purchase #4 $70.25   12.626%   $79.1198   $79.12   $79.10   $79.10  
  Purchase #5 $237.26   7.616%   $255.3297   $255.33   $255.35   $255.30  
  Purchase #6 $93.47   6.621%   $99.6586   $99.66   $99.65   $99.70  
  Purchase #7 $196.25   4.105%   $204.3061   $204.31   $204.30   $204.30  
  7 purchase totals = $1,107.87       $1,195.6542   $1,195.66   $1,195.65   $1,195.70