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 $96.41   8.187%   $104.3031   $104.30   $104.30   $104.30  
  Purchase #2 $159.85   13.620%   $181.6216   $181.62   $181.60   $181.60  
  Purchase #3 $139.44   5.382%   $146.9447   $146.94   $146.95   $146.90  
  Purchase #4 $112.47   6.295%   $119.55   $119.55   $119.55   $119.60  
  Purchase #5 $250.49   3.846%   $260.1238   $260.12   $260.10   $260.10  
  Purchase #6 $202.28   4.753%   $211.8944   $211.89   $211.90   $211.90  
  Purchase #7 $34.44   11.775%   $38.4953   $38.50   $38.50   $38.50  
  7 purchase totals = $995.38       $1,062.9329   $1,062.92   $1,062.90   $1,062.90