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 $184.40   11.636%   $205.8568   $205.86   $205.85   $205.90  
  Purchase #2 $193.58   7.253%   $207.6204   $207.62   $207.60   $207.60  
  Purchase #3 $173.77   13.182%   $196.6764   $196.68   $196.70   $196.70  
  Purchase #4 $117.61   7.577%   $126.5213   $126.52   $126.50   $126.50  
  Purchase #5 $21.53   13.377%   $24.4101   $24.41   $24.40   $24.40  
  Purchase #6 $98.97   6.778%   $105.6782   $105.68   $105.70   $105.70  
  Purchase #7 $245.67   9.368%   $268.6844   $268.68   $268.70   $268.70  
  7 purchase totals = $1,035.53       $1,135.4476   $1,135.45   $1,135.45   $1,135.50