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 $22.98   13.250%   $26.0249   $26.02   $26.00   $26.00  
  Purchase #2 $196.68   3.814%   $204.1814   $204.18   $204.20   $204.20  
  Purchase #3 $167.85   13.236%   $190.0666   $190.07   $190.05   $190.10  
  Purchase #4 $10.55   10.152%   $11.621   $11.62   $11.60   $11.60  
  Purchase #5 $226.79   5.735%   $239.7964   $239.80   $239.80   $239.80  
  Purchase #6 $129.60   10.634%   $143.3817   $143.38   $143.40   $143.40  
  Purchase #7 $33.83   4.361%   $35.3053   $35.31   $35.30   $35.30  
  7 purchase totals = $788.28       $850.3773   $850.38   $850.35   $850.40