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 $214.86   8.614%   $233.368   $233.37   $233.35   $233.40  
  Purchase #2 $236.59   7.153%   $253.5133   $253.51   $253.50   $253.50  
  Purchase #3 $213.77   4.432%   $223.2443   $223.24   $223.25   $223.20  
  Purchase #4 $90.81   12.724%   $102.3647   $102.36   $102.35   $102.40  
  Purchase #5 $155.74   4.213%   $162.3013   $162.30   $162.30   $162.30  
  Purchase #6 $25.38   11.431%   $28.2812   $28.28   $28.30   $28.30  
  Purchase #7 $147.41   10.686%   $163.1622   $163.16   $163.15   $163.20  
  7 purchase totals = $1,084.56       $1,166.2350   $1,166.22   $1,166.20   $1,166.30