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 $195.93   7.685%   $210.9872   $210.99   $211.00   $211.00  
  Purchase #2 $125.89   12.558%   $141.6993   $141.70   $141.70   $141.70  
  Purchase #3 $21.86   5.128%   $22.981   $22.98   $23.00   $23.00  
  Purchase #4 $214.44   6.770%   $228.9576   $228.96   $228.95   $229.00  
  Purchase #5 $133.67   7.756%   $144.0374   $144.04   $144.05   $144.00  
  Purchase #6 $204.49   3.634%   $211.9212   $211.92   $211.90   $211.90  
  Purchase #7 $100.68   3.562%   $104.2662   $104.27   $104.25   $104.30  
  7 purchase totals = $996.96       $1,064.8499   $1,064.86   $1,064.85   $1,064.90