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 $104.76   7.585%   $112.706   $112.71   $112.70   $112.70  
  Purchase #2 $240.29   7.461%   $258.218   $258.22   $258.20   $258.20  
  Purchase #3 $67.59   11.102%   $75.0938   $75.09   $75.10   $75.10  
  Purchase #4 $164.34   8.277%   $177.9424   $177.94   $177.95   $177.90  
  Purchase #5 $146.54   13.479%   $166.2921   $166.29   $166.30   $166.30  
  Purchase #6 $150.55   6.364%   $160.131   $160.13   $160.15   $160.10  
  Purchase #7 $146.85   6.599%   $156.5406   $156.54   $156.55   $156.50  
  7 purchase totals = $1,020.92       $1,106.9239   $1,106.92   $1,106.95   $1,106.80