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 $72.86   6.492%   $77.5901   $77.59   $77.60   $77.60  
  Purchase #2 $248.40   6.279%   $263.997   $264.00   $264.00   $264.00  
  Purchase #3 $169.34   10.205%   $186.6211   $186.62   $186.60   $186.60  
  Purchase #4 $101.63   8.526%   $110.295   $110.30   $110.30   $110.30  
  Purchase #5 $149.73   4.760%   $156.8571   $156.86   $156.85   $156.90  
  Purchase #6 $49.63   7.451%   $53.3279   $53.33   $53.35   $53.30  
  Purchase #7 $199.45   5.389%   $210.1984   $210.20   $210.20   $210.20  
  7 purchase totals = $991.04       $1,058.8866   $1,058.90   $1,058.90   $1,058.90