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 $180.33   8.659%   $195.9448   $195.94   $195.95   $195.90  
  Purchase #2 $237.47   12.714%   $267.6619   $267.66   $267.65   $267.70  
  Purchase #3 $141.68   10.592%   $156.6867   $156.69   $156.70   $156.70  
  Purchase #4 $51.51   11.140%   $57.2482   $57.25   $57.25   $57.20  
  Purchase #5 $117.31   6.745%   $125.2226   $125.22   $125.20   $125.20  
  Purchase #6 $204.92   7.757%   $220.8156   $220.82   $220.80   $220.80  
  Purchase #7 $100.82   4.138%   $104.9919   $104.99   $105.00   $105.00  
  7 purchase totals = $1,034.04       $1,128.5717   $1,128.57   $1,128.55   $1,128.50