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 $246.43   4.602%   $257.7707   $257.77   $257.75   $257.80  
  Purchase #2 $250.75   4.113%   $261.0633   $261.06   $261.05   $261.10  
  Purchase #3 $129.90   10.227%   $143.1849   $143.18   $143.20   $143.20  
  Purchase #4 $81.67   4.125%   $85.0389   $85.04   $85.05   $85.00  
  Purchase #5 $69.36   10.194%   $76.4306   $76.43   $76.45   $76.40  
  Purchase #6 $194.79   4.736%   $204.0153   $204.02   $204.00   $204.00  
  Purchase #7 $226.57   3.481%   $234.4569   $234.46   $234.45   $234.50  
  7 purchase totals = $1,199.47       $1,261.9606   $1,261.96   $1,261.95   $1,262.00