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 $194.62   7.383%   $208.9888   $208.99   $209.00   $209.00  
  Purchase #2 $248.55   5.821%   $263.0181   $263.02   $263.00   $263.00  
  Purchase #3 $216.29   8.117%   $233.8463   $233.85   $233.85   $233.80  
  Purchase #4 $5.26   8.577%   $5.7112   $5.71   $5.70   $5.70  
  Purchase #5 $54.43   9.409%   $59.5513   $59.55   $59.55   $59.60  
  Purchase #6 $160.58   4.238%   $167.3854   $167.39   $167.40   $167.40  
  Purchase #7 $188.86   10.492%   $208.6752   $208.68   $208.70   $208.70  
  7 purchase totals = $1,068.59       $1,147.1763   $1,147.19   $1,147.20   $1,147.20