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 $65.61   11.305%   $73.0272   $73.03   $73.05   $73.00  
  Purchase #2 $225.77   9.183%   $246.5025   $246.50   $246.50   $246.50  
  Purchase #3 $112.88   12.744%   $127.2654   $127.27   $127.25   $127.30  
  Purchase #4 $220.96   6.683%   $235.7268   $235.73   $235.75   $235.70  
  Purchase #5 $121.60   4.600%   $127.1936   $127.19   $127.20   $127.20  
  Purchase #6 $188.42   10.229%   $207.6935   $207.69   $207.70   $207.70  
  Purchase #7 $139.84   6.669%   $149.1659   $149.17   $149.15   $149.20  
  7 purchase totals = $1,075.08       $1,166.5749   $1,166.58   $1,166.60   $1,166.60