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 $196.26   8.833%   $213.5956   $213.60   $213.60   $213.60  
  Purchase #2 $59.47   7.185%   $63.7429   $63.74   $63.75   $63.70  
  Purchase #3 $84.74   9.789%   $93.0352   $93.04   $93.05   $93.00  
  Purchase #4 $192.41   3.269%   $198.6999   $198.70   $198.70   $198.70  
  Purchase #5 $198.94   11.764%   $222.3433   $222.34   $222.35   $222.30  
  Purchase #6 $172.92   3.128%   $178.3289   $178.33   $178.35   $178.30  
  Purchase #7 $47.67   13.688%   $54.1951   $54.20   $54.20   $54.20  
  7 purchase totals = $952.41       $1,023.9409   $1,023.95   $1,024.00   $1,023.80