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 $58.52   8.660%   $63.5878   $63.59   $63.60   $63.60  
  Purchase #2 $187.97   4.538%   $196.5001   $196.50   $196.50   $196.50  
  Purchase #3 $84.95   10.750%   $94.0821   $94.08   $94.10   $94.10  
  Purchase #4 $183.99   5.695%   $194.4682   $194.47   $194.45   $194.50  
  Purchase #5 $228.28   3.540%   $236.3611   $236.36   $236.35   $236.40  
  Purchase #6 $74.57   11.441%   $83.1016   $83.10   $83.10   $83.10  
  Purchase #7 $116.75   13.131%   $132.0804   $132.08   $132.10   $132.10  
  7 purchase totals = $935.03       $1,000.1813   $1,000.18   $1,000.20   $1,000.30