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 $140.89   7.501%   $151.4582   $151.46   $151.45   $151.50  
  Purchase #2 $148.26   11.492%   $165.298   $165.30   $165.30   $165.30  
  Purchase #3 $86.95   10.573%   $96.1432   $96.14   $96.15   $96.10  
  Purchase #4 $34.71   11.116%   $38.5684   $38.57   $38.55   $38.60  
  Purchase #5 $59.46   8.384%   $64.4451   $64.45   $64.45   $64.40  
  Purchase #6 $227.87   7.406%   $244.7461   $244.75   $244.75   $244.70  
  Purchase #7 $248.93   6.841%   $265.9593   $265.96   $265.95   $266.00  
  7 purchase totals = $947.07       $1,026.6183   $1,026.63   $1,026.60   $1,026.60