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 $208.41   13.505%   $236.5558   $236.56   $236.55   $236.60  
  Purchase #2 $13.78   4.407%   $14.3873   $14.39   $14.40   $14.40  
  Purchase #3 $233.95   7.526%   $251.5571   $251.56   $251.55   $251.60  
  Purchase #4 $170.83   5.644%   $180.4716   $180.47   $180.45   $180.50  
  Purchase #5 $195.56   4.198%   $203.7696   $203.77   $203.75   $203.80  
  Purchase #6 $56.98   13.631%   $64.7469   $64.75   $64.75   $64.70  
  Purchase #7 $190.93   9.840%   $209.7175   $209.72   $209.70   $209.70  
  7 purchase totals = $1,070.44       $1,161.2058   $1,161.22   $1,161.15   $1,161.30