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 $210.60   6.852%   $225.0303   $225.03   $225.05   $225.00  
  Purchase #2 $127.93   11.781%   $143.0014   $143.00   $143.00   $143.00  
  Purchase #3 $117.39   5.104%   $123.3816   $123.38   $123.40   $123.40  
  Purchase #4 $69.43   10.750%   $76.8937   $76.89   $76.90   $76.90  
  Purchase #5 $74.40   5.446%   $78.4518   $78.45   $78.45   $78.50  
  Purchase #6 $245.97   12.403%   $276.4777   $276.48   $276.50   $276.50  
  Purchase #7 $198.97   6.651%   $212.2035   $212.20   $212.20   $212.20  
  7 purchase totals = $1,044.69       $1,135.4400   $1,135.43   $1,135.50   $1,135.50