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 $214.26   8.712%   $232.9263   $232.93   $232.95   $232.90  
  Purchase #2 $225.82   7.136%   $241.9345   $241.93   $241.95   $241.90  
  Purchase #3 $103.58   10.767%   $114.7325   $114.73   $114.75   $114.70  
  Purchase #4 $225.38   7.692%   $242.7162   $242.72   $242.70   $242.70  
  Purchase #5 $111.86   5.167%   $117.6398   $117.64   $117.65   $117.60  
  Purchase #6 $158.43   10.270%   $174.7008   $174.70   $174.70   $174.70  
  Purchase #7 $180.85   6.136%   $191.947   $191.95   $191.95   $191.90  
  7 purchase totals = $1,220.18       $1,316.5971   $1,316.60   $1,316.65   $1,316.40