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 $33.54   7.551%   $36.0726   $36.07   $36.05   $36.10  
  Purchase #2 $238.53   11.446%   $265.8321   $265.83   $265.85   $265.80  
  Purchase #3 $55.96   11.515%   $62.4038   $62.40   $62.40   $62.40  
  Purchase #4 $75.49   4.256%   $78.7029   $78.70   $78.70   $78.70  
  Purchase #5 $206.86   7.844%   $223.0861   $223.09   $223.10   $223.10  
  Purchase #6 $15.66   5.543%   $16.528   $16.53   $16.55   $16.50  
  Purchase #7 $71.74   4.481%   $74.9547   $74.95   $74.95   $75.00  
  7 purchase totals = $697.78       $757.5802   $757.57   $757.60   $757.60