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 $216.44   6.551%   $230.619   $230.62   $230.60   $230.60  
  Purchase #2 $77.43   11.684%   $86.4769   $86.48   $86.50   $86.50  
  Purchase #3 $225.61   10.224%   $248.6764   $248.68   $248.70   $248.70  
  Purchase #4 $152.36   9.148%   $166.2979   $166.30   $166.30   $166.30  
  Purchase #5 $234.75   6.619%   $250.2881   $250.29   $250.30   $250.30  
  Purchase #6 $246.32   13.640%   $279.918   $279.92   $279.90   $279.90  
  Purchase #7 $195.62   11.594%   $218.3002   $218.30   $218.30   $218.30  
  7 purchase totals = $1,348.53       $1,480.5765   $1,480.59   $1,480.60   $1,480.60