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 $59.95   3.241%   $61.893   $61.89   $61.90   $61.90  
  Purchase #2 $212.40   6.450%   $226.0998   $226.10   $226.10   $226.10  
  Purchase #3 $96.84   10.403%   $106.9143   $106.91   $106.90   $106.90  
  Purchase #4 $240.42   10.301%   $265.1857   $265.19   $265.20   $265.20  
  Purchase #5 $123.78   12.395%   $139.1225   $139.12   $139.10   $139.10  
  Purchase #6 $218.50   9.705%   $239.7054   $239.71   $239.70   $239.70  
  Purchase #7 $64.62   5.464%   $68.1508   $68.15   $68.15   $68.20  
  7 purchase totals = $1,016.51       $1,107.0715   $1,107.07   $1,107.05   $1,107.10