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 $58.44   5.448%   $61.6238   $61.62   $61.60   $61.60  
  Purchase #2 $178.79   5.422%   $188.484   $188.48   $188.50   $188.50  
  Purchase #3 $25.49   4.202%   $26.5611   $26.56   $26.55   $26.60  
  Purchase #4 $125.93   8.434%   $136.5509   $136.55   $136.55   $136.60  
  Purchase #5 $100.40   4.171%   $104.5877   $104.59   $104.60   $104.60  
  Purchase #6 $134.64   9.312%   $147.1777   $147.18   $147.20   $147.20  
  Purchase #7 $207.36   6.216%   $220.2495   $220.25   $220.25   $220.20  
  7 purchase totals = $831.05       $885.2347   $885.23   $885.25   $885.30