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 $210.69   7.104%   $225.6574   $225.66   $225.65   $225.70  
  Purchase #2 $23.88   9.336%   $26.1094   $26.11   $26.10   $26.10  
  Purchase #3 $242.70   7.145%   $260.0409   $260.04   $260.05   $260.00  
  Purchase #4 $117.57   4.362%   $122.6984   $122.70   $122.70   $122.70  
  Purchase #5 $139.79   10.597%   $154.6035   $154.60   $154.60   $154.60  
  Purchase #6 $121.66   5.146%   $127.9206   $127.92   $127.90   $127.90  
  Purchase #7 $43.57   5.451%   $45.945   $45.95   $45.95   $45.90  
  7 purchase totals = $899.86       $962.9752   $962.98   $962.95   $962.90