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 $198.51   8.873%   $216.1238   $216.12   $216.10   $216.10  
  Purchase #2 $236.82   7.205%   $253.8829   $253.88   $253.90   $253.90  
  Purchase #3 $71.57   13.301%   $81.0895   $81.09   $81.10   $81.10  
  Purchase #4 $234.28   7.735%   $252.4016   $252.40   $252.40   $252.40  
  Purchase #5 $49.85   13.734%   $56.6964   $56.70   $56.70   $56.70  
  Purchase #6 $201.39   13.383%   $228.342   $228.34   $228.35   $228.30  
  Purchase #7 $157.95   10.801%   $175.0102   $175.01   $175.00   $175.00  
  7 purchase totals = $1,150.37       $1,263.5464   $1,263.54   $1,263.55   $1,263.50