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 $127.87   12.262%   $143.5494   $143.55   $143.55   $143.50  
  Purchase #2 $148.92   13.419%   $168.9036   $168.90   $168.90   $168.90  
  Purchase #3 $119.61   6.722%   $127.6502   $127.65   $127.65   $127.70  
  Purchase #4 $190.72   9.422%   $208.6896   $208.69   $208.70   $208.70  
  Purchase #5 $76.57   13.282%   $86.74   $86.74   $86.75   $86.70  
  Purchase #6 $195.56   6.353%   $207.9839   $207.98   $208.00   $208.00  
  Purchase #7 $176.28   3.194%   $181.9104   $181.91   $181.90   $181.90  
  7 purchase totals = $1,035.53       $1,125.4271   $1,125.42   $1,125.45   $1,125.40