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 $195.44   9.630%   $214.2609   $214.26   $214.25   $214.30  
  Purchase #2 $63.46   7.163%   $68.0056   $68.01   $68.00   $68.00  
  Purchase #3 $233.73   13.321%   $264.8652   $264.87   $264.85   $264.90  
  Purchase #4 $137.47   4.803%   $144.0727   $144.07   $144.05   $144.10  
  Purchase #5 $19.25   4.119%   $20.0429   $20.04   $20.05   $20.00  
  Purchase #6 $241.45   6.241%   $256.5189   $256.52   $256.50   $256.50  
  Purchase #7 $62.47   8.213%   $67.6007   $67.60   $67.60   $67.60  
  7 purchase totals = $953.27       $1,035.3669   $1,035.37   $1,035.30   $1,035.40