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 $118.56   6.237%   $125.9546   $125.95   $125.95   $126.00  
  Purchase #2 $68.45   9.698%   $75.0883   $75.09   $75.10   $75.10  
  Purchase #3 $167.90   12.689%   $189.2048   $189.20   $189.20   $189.20  
  Purchase #4 $159.31   12.346%   $178.9784   $178.98   $179.00   $179.00  
  Purchase #5 $163.81   11.750%   $183.0577   $183.06   $183.05   $183.10  
  Purchase #6 $78.64   10.491%   $86.8901   $86.89   $86.90   $86.90  
  Purchase #7 $208.54   10.134%   $229.6734   $229.67   $229.65   $229.70  
  7 purchase totals = $965.21       $1,068.8473   $1,068.84   $1,068.85   $1,069.00