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 $61.34   11.460%   $68.3696   $68.37   $68.35   $68.40  
  Purchase #2 $200.89   7.868%   $216.696   $216.70   $216.70   $216.70  
  Purchase #3 $17.54   6.119%   $18.6133   $18.61   $18.60   $18.60  
  Purchase #4 $246.98   8.393%   $267.709   $267.71   $267.70   $267.70  
  Purchase #5 $93.67   12.599%   $105.4715   $105.47   $105.45   $105.50  
  Purchase #6 $144.50   12.135%   $162.0351   $162.04   $162.05   $162.00  
  Purchase #7 $220.76   12.317%   $247.951   $247.95   $247.95   $248.00  
  7 purchase totals = $985.68       $1,086.8455   $1,086.85   $1,086.80   $1,086.90