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 $91.95   3.594%   $95.2547   $95.25   $95.25   $95.30  
  Purchase #2 $232.33   8.660%   $252.4498   $252.45   $252.45   $252.40  
  Purchase #3 $51.56   12.707%   $58.1117   $58.11   $58.10   $58.10  
  Purchase #4 $181.74   6.664%   $193.8512   $193.85   $193.85   $193.90  
  Purchase #5 $132.87   9.228%   $145.1312   $145.13   $145.15   $145.10  
  Purchase #6 $229.70   8.142%   $248.4022   $248.40   $248.40   $248.40  
  Purchase #7 $63.92   13.394%   $72.4814   $72.48   $72.50   $72.50  
  7 purchase totals = $984.07       $1,065.6822   $1,065.67   $1,065.70   $1,065.70