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 $83.33   12.737%   $93.9437   $93.94   $93.95   $93.90  
  Purchase #2 $190.76   9.537%   $208.9528   $208.95   $208.95   $209.00  
  Purchase #3 $191.80   10.451%   $211.845   $211.85   $211.85   $211.80  
  Purchase #4 $161.67   6.487%   $172.1575   $172.16   $172.15   $172.20  
  Purchase #5 $63.37   5.825%   $67.0613   $67.06   $67.05   $67.10  
  Purchase #6 $223.84   3.416%   $231.4864   $231.49   $231.50   $231.50  
  Purchase #7 $187.62   11.808%   $209.7742   $209.77   $209.75   $209.80  
  7 purchase totals = $1,102.39       $1,195.2209   $1,195.22   $1,195.20   $1,195.30