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 $232.37   5.274%   $244.6252   $244.63   $244.65   $244.60  
  Purchase #2 $195.60   10.833%   $216.7893   $216.79   $216.80   $216.80  
  Purchase #3 $103.63   6.685%   $110.5577   $110.56   $110.55   $110.60  
  Purchase #4 $144.29   8.619%   $156.7264   $156.73   $156.75   $156.70  
  Purchase #5 $209.97   3.106%   $216.4917   $216.49   $216.50   $216.50  
  Purchase #6 $110.77   10.382%   $122.2701   $122.27   $122.25   $122.30  
  Purchase #7 $24.81   8.687%   $26.9652   $26.97   $26.95   $27.00  
  7 purchase totals = $1,021.44       $1,094.4256   $1,094.44   $1,094.45   $1,094.50