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 $181.70   9.405%   $198.7889   $198.79   $198.80   $198.80  
  Purchase #2 $195.79   11.829%   $218.95   $218.95   $218.95   $219.00  
  Purchase #3 $68.27   11.288%   $75.9763   $75.98   $76.00   $76.00  
  Purchase #4 $85.51   8.839%   $93.0682   $93.07   $93.05   $93.10  
  Purchase #5 $187.76   11.214%   $208.8154   $208.82   $208.80   $208.80  
  Purchase #6 $75.66   3.267%   $78.1318   $78.13   $78.15   $78.10  
  Purchase #7 $157.58   10.694%   $174.4316   $174.43   $174.45   $174.40  
  7 purchase totals = $952.27       $1,048.1622   $1,048.17   $1,048.20   $1,048.20