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 $162.26   8.801%   $176.5405   $176.54   $176.55   $176.50  
  Purchase #2 $92.56   3.669%   $95.956   $95.96   $95.95   $96.00  
  Purchase #3 $139.73   7.167%   $149.7444   $149.74   $149.75   $149.70  
  Purchase #4 $162.84   6.846%   $173.988   $173.99   $174.00   $174.00  
  Purchase #5 $115.46   8.749%   $125.5616   $125.56   $125.55   $125.60  
  Purchase #6 $33.62   8.778%   $36.5712   $36.57   $36.55   $36.60  
  Purchase #7 $193.72   4.649%   $202.726   $202.73   $202.75   $202.70  
  7 purchase totals = $900.19       $961.0877   $961.09   $961.10   $961.10