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 $59.60   5.832%   $63.0759   $63.08   $63.10   $63.10  
  Purchase #2 $232.98   12.415%   $261.9045   $261.90   $261.90   $261.90  
  Purchase #3 $62.34   7.244%   $66.8559   $66.86   $66.85   $66.90  
  Purchase #4 $35.41   11.621%   $39.525   $39.53   $39.55   $39.50  
  Purchase #5 $224.92   4.734%   $235.5677   $235.57   $235.55   $235.60  
  Purchase #6 $207.94   8.492%   $225.5983   $225.60   $225.60   $225.60  
  Purchase #7 $153.77   7.660%   $165.5488   $165.55   $165.55   $165.50  
  7 purchase totals = $976.96       $1,058.0761   $1,058.09   $1,058.10   $1,058.10