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 $105.96   12.810%   $119.5335   $119.53   $119.55   $119.50  
  Purchase #2 $105.99   11.411%   $118.0845   $118.08   $118.10   $118.10  
  Purchase #3 $137.87   11.332%   $153.4934   $153.49   $153.50   $153.50  
  Purchase #4 $214.91   6.357%   $228.5718   $228.57   $228.55   $228.60  
  Purchase #5 $187.39   6.420%   $199.4204   $199.42   $199.40   $199.40  
  Purchase #6 $167.86   3.356%   $173.4934   $173.49   $173.50   $173.50  
  Purchase #7 $187.36   11.302%   $208.5354   $208.54   $208.55   $208.50  
  7 purchase totals = $1,107.34       $1,201.1324   $1,201.12   $1,201.15   $1,201.10