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 $156.34   11.271%   $173.9611   $173.96   $173.95   $174.00  
  Purchase #2 $94.52   9.387%   $103.3926   $103.39   $103.40   $103.40  
  Purchase #3 $220.88   5.829%   $233.7551   $233.76   $233.75   $233.80  
  Purchase #4 $246.82   3.702%   $255.9573   $255.96   $255.95   $256.00  
  Purchase #5 $73.39   11.729%   $81.9979   $82.00   $82.00   $82.00  
  Purchase #6 $247.83   5.682%   $261.9117   $261.91   $261.90   $261.90  
  Purchase #7 $213.97   7.675%   $230.3922   $230.39   $230.40   $230.40  
  7 purchase totals = $1,253.75       $1,341.3679   $1,341.37   $1,341.35   $1,341.50