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 $58.79   7.258%   $63.057   $63.06   $63.05   $63.10  
  Purchase #2 $20.39   13.520%   $23.1467   $23.15   $23.15   $23.10  
  Purchase #3 $201.41   7.210%   $215.9317   $215.93   $215.95   $215.90  
  Purchase #4 $174.72   4.612%   $182.7781   $182.78   $182.80   $182.80  
  Purchase #5 $196.31   8.320%   $212.643   $212.64   $212.65   $212.60  
  Purchase #6 $21.33   7.741%   $22.9812   $22.98   $23.00   $23.00  
  Purchase #7 $5.44   12.874%   $6.1403   $6.14   $6.15   $6.10  
  7 purchase totals = $678.39       $726.6780   $726.68   $726.75   $726.60