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 $167.25   11.786%   $186.9621   $186.96   $186.95   $187.00  
  Purchase #2 $106.28   9.747%   $116.6391   $116.64   $116.65   $116.60  
  Purchase #3 $58.60   4.219%   $61.0723   $61.07   $61.05   $61.10  
  Purchase #4 $77.65   6.128%   $82.4084   $82.41   $82.40   $82.40  
  Purchase #5 $219.87   6.712%   $234.6277   $234.63   $234.65   $234.60  
  Purchase #6 $14.84   4.472%   $15.5036   $15.50   $15.50   $15.50  
  Purchase #7 $225.67   8.380%   $244.5811   $244.58   $244.60   $244.60  
  7 purchase totals = $870.16       $941.7943   $941.79   $941.80   $941.80