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 $183.28   6.775%   $195.6972   $195.70   $195.70   $195.70  
  Purchase #2 $201.72   8.250%   $218.3619   $218.36   $218.35   $218.40  
  Purchase #3 $176.50   11.256%   $196.3668   $196.37   $196.35   $196.40  
  Purchase #4 $51.99   12.460%   $58.468   $58.47   $58.45   $58.50  
  Purchase #5 $148.41   13.394%   $168.288   $168.29   $168.30   $168.30  
  Purchase #6 $250.51   6.710%   $267.3192   $267.32   $267.30   $267.30  
  Purchase #7 $214.49   8.229%   $232.1404   $232.14   $232.15   $232.10  
  7 purchase totals = $1,226.90       $1,336.6415   $1,336.65   $1,336.60   $1,336.70