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 $60.54   3.835%   $62.8617   $62.86   $62.85   $62.90  
  Purchase #2 $203.77   11.717%   $227.6457   $227.65   $227.65   $227.60  
  Purchase #3 $246.28   7.272%   $264.1895   $264.19   $264.20   $264.20  
  Purchase #4 $166.50   13.623%   $189.1823   $189.18   $189.20   $189.20  
  Purchase #5 $21.87   6.591%   $23.3115   $23.31   $23.30   $23.30  
  Purchase #6 $109.81   5.415%   $115.7562   $115.76   $115.75   $115.80  
  Purchase #7 $231.43   7.177%   $248.0397   $248.04   $248.05   $248.00  
  7 purchase totals = $1,040.20       $1,130.9866   $1,130.99   $1,131.00   $1,131.00