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 $42.26   9.684%   $46.3525   $46.35   $46.35   $46.40  
  Purchase #2 $26.93   7.738%   $29.0138   $29.01   $29.00   $29.00  
  Purchase #3 $106.41   11.512%   $118.6599   $118.66   $118.65   $118.70  
  Purchase #4 $61.88   5.252%   $65.1299   $65.13   $65.15   $65.10  
  Purchase #5 $240.66   8.431%   $260.95   $260.95   $260.95   $261.00  
  Purchase #6 $224.36   8.482%   $243.3902   $243.39   $243.40   $243.40  
  Purchase #7 $239.63   9.122%   $261.489   $261.49   $261.50   $261.50  
  7 purchase totals = $942.13       $1,024.9853   $1,024.98   $1,025.00   $1,025.10