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 $148.76   12.729%   $167.6957   $167.70   $167.70   $167.70  
  Purchase #2 $24.77   13.761%   $28.1786   $28.18   $28.20   $28.20  
  Purchase #3 $97.56   7.663%   $105.036   $105.04   $105.05   $105.00  
  Purchase #4 $111.85   5.492%   $117.9928   $117.99   $118.00   $118.00  
  Purchase #5 $182.71   5.483%   $192.728   $192.73   $192.75   $192.70  
  Purchase #6 $187.54   4.119%   $195.2648   $195.26   $195.25   $195.30  
  Purchase #7 $220.62   12.650%   $248.5284   $248.53   $248.55   $248.50  
  7 purchase totals = $973.81       $1,055.4243   $1,055.43   $1,055.50   $1,055.40