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 $83.68   13.520%   $94.9935   $94.99   $95.00   $95.00  
  Purchase #2 $147.40   9.476%   $161.3676   $161.37   $161.35   $161.40  
  Purchase #3 $196.30   5.239%   $206.5842   $206.58   $206.60   $206.60  
  Purchase #4 $89.40   10.369%   $98.6699   $98.67   $98.65   $98.70  
  Purchase #5 $189.58   6.519%   $201.9387   $201.94   $201.95   $201.90  
  Purchase #6 $227.79   5.336%   $239.9449   $239.94   $239.95   $239.90  
  Purchase #7 $7.95   5.604%   $8.3955   $8.40   $8.40   $8.40  
  7 purchase totals = $942.10       $1,011.8943   $1,011.89   $1,011.90   $1,011.90