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 $31.72   12.348%   $35.6368   $35.64   $35.65   $35.60  
  Purchase #2 $59.63   5.208%   $62.7355   $62.74   $62.75   $62.70  
  Purchase #3 $113.91   10.738%   $126.1417   $126.14   $126.15   $126.10  
  Purchase #4 $192.47   9.735%   $211.207   $211.21   $211.20   $211.20  
  Purchase #5 $117.67   8.341%   $127.4849   $127.48   $127.50   $127.50  
  Purchase #6 $245.59   8.721%   $267.0079   $267.01   $267.00   $267.00  
  Purchase #7 $213.42   7.642%   $229.7296   $229.73   $229.75   $229.70  
  7 purchase totals = $974.41       $1,059.9434   $1,059.95   $1,060.00   $1,059.80