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 $62.89   9.255%   $68.7105   $68.71   $68.70   $68.70  
  Purchase #2 $86.57   13.715%   $98.4431   $98.44   $98.45   $98.40  
  Purchase #3 $17.81   8.869%   $19.3896   $19.39   $19.40   $19.40  
  Purchase #4 $50.77   6.303%   $53.97   $53.97   $53.95   $54.00  
  Purchase #5 $229.35   5.381%   $241.6913   $241.69   $241.70   $241.70  
  Purchase #6 $160.64   10.619%   $177.6984   $177.70   $177.70   $177.70  
  Purchase #7 $84.78   12.422%   $95.3114   $95.31   $95.30   $95.30  
  7 purchase totals = $692.81       $755.2143   $755.21   $755.20   $755.20