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 $188.25   5.830%   $199.225   $199.23   $199.25   $199.20  
  Purchase #2 $61.31   7.638%   $65.9929   $65.99   $66.00   $66.00  
  Purchase #3 $16.39   7.247%   $17.5778   $17.58   $17.60   $17.60  
  Purchase #4 $169.50   3.836%   $176.002   $176.00   $176.00   $176.00  
  Purchase #5 $202.64   9.129%   $221.139   $221.14   $221.15   $221.10  
  Purchase #6 $78.32   7.486%   $84.183   $84.18   $84.20   $84.20  
  Purchase #7 $250.54   3.361%   $258.9606   $258.96   $258.95   $259.00  
  7 purchase totals = $966.95       $1,023.0803   $1,023.08   $1,023.15   $1,023.10