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 $63.31   12.370%   $71.1414   $71.14   $71.15   $71.10  
  Purchase #2 $227.82   3.130%   $234.9508   $234.95   $234.95   $235.00  
  Purchase #3 $8.66   9.210%   $9.4576   $9.46   $9.45   $9.50  
  Purchase #4 $204.70   13.835%   $233.0202   $233.02   $233.00   $233.00  
  Purchase #5 $37.74   5.293%   $39.7376   $39.74   $39.75   $39.70  
  Purchase #6 $237.26   10.180%   $261.4131   $261.41   $261.40   $261.40  
  Purchase #7 $67.75   13.670%   $77.0114   $77.01   $77.00   $77.00  
  7 purchase totals = $847.24       $926.7321   $926.73   $926.70   $926.70