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 $62.27   3.767%   $64.6157   $64.62   $64.60   $64.60  
  Purchase #2 $34.73   10.828%   $38.4906   $38.49   $38.50   $38.50  
  Purchase #3 $171.33   4.237%   $178.5893   $178.59   $178.60   $178.60  
  Purchase #4 $195.93   6.292%   $208.2579   $208.26   $208.25   $208.30  
  Purchase #5 $129.93   3.154%   $134.028   $134.03   $134.05   $134.00  
  Purchase #6 $245.50   12.818%   $276.9682   $276.97   $276.95   $277.00  
  Purchase #7 $193.45   8.703%   $210.286   $210.29   $210.30   $210.30  
  7 purchase totals = $1,033.14       $1,111.2357   $1,111.25   $1,111.25   $1,111.30