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 $107.64   5.858%   $113.9456   $113.95   $113.95   $113.90  
  Purchase #2 $163.43   5.584%   $172.5559   $172.56   $172.55   $172.60  
  Purchase #3 $152.41   8.234%   $164.9594   $164.96   $164.95   $165.00  
  Purchase #4 $23.96   6.156%   $25.435   $25.44   $25.45   $25.40  
  Purchase #5 $155.79   13.386%   $176.644   $176.64   $176.65   $176.60  
  Purchase #6 $243.41   7.339%   $261.2739   $261.27   $261.25   $261.30  
  Purchase #7 $33.96   3.573%   $35.1734   $35.17   $35.15   $35.20  
  7 purchase totals = $880.60       $949.9872   $949.99   $949.95   $950.00