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 $103.96   12.791%   $117.2575   $117.26   $117.25   $117.30  
  Purchase #2 $213.88   10.501%   $236.3395   $236.34   $236.35   $236.30  
  Purchase #3 $150.46   6.730%   $160.586   $160.59   $160.60   $160.60  
  Purchase #4 $93.94   4.769%   $98.42   $98.42   $98.40   $98.40  
  Purchase #5 $182.98   9.690%   $200.7108   $200.71   $200.70   $200.70  
  Purchase #6 $181.92   7.874%   $196.2444   $196.24   $196.25   $196.20  
  Purchase #7 $105.81   9.592%   $115.9593   $115.96   $115.95   $116.00  
  7 purchase totals = $1,032.95       $1,125.5175   $1,125.52   $1,125.50   $1,125.50