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 $83.62   10.110%   $92.074   $92.07   $92.05   $92.10  
  Purchase #2 $137.67   13.329%   $156.02   $156.02   $156.00   $156.00  
  Purchase #3 $232.97   12.253%   $261.5158   $261.52   $261.50   $261.50  
  Purchase #4 $204.96   13.702%   $233.0436   $233.04   $233.05   $233.00  
  Purchase #5 $180.72   3.168%   $186.4452   $186.45   $186.45   $186.40  
  Purchase #6 $162.88   9.469%   $178.3031   $178.30   $178.30   $178.30  
  Purchase #7 $139.25   9.272%   $152.1613   $152.16   $152.15   $152.20  
  7 purchase totals = $1,142.07       $1,259.5630   $1,259.56   $1,259.50   $1,259.50