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 $209.25   11.613%   $233.5502   $233.55   $233.55   $233.60  
  Purchase #2 $210.50   12.553%   $236.9241   $236.92   $236.90   $236.90  
  Purchase #3 $17.44   4.232%   $18.1781   $18.18   $18.20   $18.20  
  Purchase #4 $122.93   9.369%   $134.4473   $134.45   $134.45   $134.40  
  Purchase #5 $216.64   12.230%   $243.1351   $243.14   $243.15   $243.10  
  Purchase #6 $59.76   13.305%   $67.7111   $67.71   $67.70   $67.70  
  Purchase #7 $219.47   6.241%   $233.1671   $233.17   $233.15   $233.20  
  7 purchase totals = $1,055.99       $1,167.1130   $1,167.12   $1,167.10   $1,167.10