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 $210.58   11.467%   $234.7272   $234.73   $234.75   $234.70  
  Purchase #2 $188.62   10.455%   $208.3402   $208.34   $208.35   $208.30  
  Purchase #3 $146.38   12.731%   $165.0156   $165.02   $165.00   $165.00  
  Purchase #4 $163.53   9.845%   $179.6295   $179.63   $179.65   $179.60  
  Purchase #5 $96.47   12.381%   $108.414   $108.41   $108.40   $108.40  
  Purchase #6 $27.74   5.821%   $29.3547   $29.35   $29.35   $29.40  
  Purchase #7 $179.74   11.508%   $200.4245   $200.42   $200.40   $200.40  
  7 purchase totals = $1,013.06       $1,125.9057   $1,125.90   $1,125.90   $1,125.80