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 $194.58   5.334%   $204.9589   $204.96   $204.95   $205.00  
  Purchase #2 $83.91   9.475%   $91.8605   $91.86   $91.85   $91.90  
  Purchase #3 $15.45   13.793%   $17.581   $17.58   $17.60   $17.60  
  Purchase #4 $229.82   13.606%   $261.0893   $261.09   $261.10   $261.10  
  Purchase #5 $244.25   11.722%   $272.881   $272.88   $272.90   $272.90  
  Purchase #6 $44.32   6.353%   $47.1356   $47.14   $47.15   $47.10  
  Purchase #7 $110.89   7.280%   $118.9628   $118.96   $118.95   $119.00  
  7 purchase totals = $923.22       $1,014.4691   $1,014.47   $1,014.50   $1,014.60