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 $134.93   5.701%   $142.6224   $142.62   $142.60   $142.60  
  Purchase #2 $244.79   5.846%   $259.1004   $259.10   $259.10   $259.10  
  Purchase #3 $218.71   11.725%   $244.3537   $244.35   $244.35   $244.40  
  Purchase #4 $14.73   3.324%   $15.2196   $15.22   $15.20   $15.20  
  Purchase #5 $192.65   4.666%   $201.639   $201.64   $201.65   $201.60  
  Purchase #6 $167.49   11.224%   $186.2891   $186.29   $186.30   $186.30  
  Purchase #7 $148.25   7.596%   $159.5111   $159.51   $159.50   $159.50  
  7 purchase totals = $1,121.55       $1,208.7353   $1,208.73   $1,208.70   $1,208.70