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 $216.86   4.482%   $226.5797   $226.58   $226.60   $226.60  
  Purchase #2 $11.97   5.656%   $12.647   $12.65   $12.65   $12.60  
  Purchase #3 $193.62   7.662%   $208.4552   $208.46   $208.45   $208.50  
  Purchase #4 $181.58   5.221%   $191.0603   $191.06   $191.05   $191.10  
  Purchase #5 $23.57   13.778%   $26.8175   $26.82   $26.80   $26.80  
  Purchase #6 $250.44   5.531%   $264.2918   $264.29   $264.30   $264.30  
  Purchase #7 $128.42   7.245%   $137.724   $137.72   $137.70   $137.70  
  7 purchase totals = $1,006.46       $1,067.5755   $1,067.58   $1,067.55   $1,067.60