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 $106.62   7.642%   $114.7679   $114.77   $114.75   $114.80  
  Purchase #2 $59.96   7.148%   $64.2459   $64.25   $64.25   $64.20  
  Purchase #3 $248.25   13.549%   $281.8854   $281.89   $281.90   $281.90  
  Purchase #4 $175.89   5.321%   $185.2491   $185.25   $185.25   $185.20  
  Purchase #5 $124.84   13.647%   $141.8769   $141.88   $141.90   $141.90  
  Purchase #6 $244.91   9.435%   $268.0173   $268.02   $268.00   $268.00  
  Purchase #7 $113.62   11.335%   $126.4988   $126.50   $126.50   $126.50  
  7 purchase totals = $1,074.09       $1,182.5413   $1,182.56   $1,182.55   $1,182.50