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 $250.58   6.697%   $267.3613   $267.36   $267.35   $267.40  
  Purchase #2 $56.80   6.633%   $60.5675   $60.57   $60.55   $60.60  
  Purchase #3 $113.29   9.288%   $123.8124   $123.81   $123.80   $123.80  
  Purchase #4 $112.75   4.137%   $117.4145   $117.41   $117.40   $117.40  
  Purchase #5 $228.71   6.274%   $243.0593   $243.06   $243.05   $243.10  
  Purchase #6 $163.71   5.195%   $172.2147   $172.21   $172.20   $172.20  
  Purchase #7 $209.96   6.165%   $222.904   $222.90   $222.90   $222.90  
  7 purchase totals = $1,135.80       $1,207.3337   $1,207.32   $1,207.25   $1,207.40