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 $113.57   3.786%   $117.8698   $117.87   $117.85   $117.90  
  Purchase #2 $57.34   8.744%   $62.3538   $62.35   $62.35   $62.40  
  Purchase #3 $229.25   3.432%   $237.1179   $237.12   $237.10   $237.10  
  Purchase #4 $209.66   11.417%   $233.5969   $233.60   $233.60   $233.60  
  Purchase #5 $212.84   7.197%   $228.1581   $228.16   $228.15   $228.20  
  Purchase #6 $244.74   7.686%   $263.5507   $263.55   $263.55   $263.60  
  Purchase #7 $231.62   9.177%   $252.8758   $252.88   $252.90   $252.90  
  7 purchase totals = $1,299.02       $1,395.5230   $1,395.53   $1,395.50   $1,395.70