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 $92.94   8.719%   $101.0434   $101.04   $101.05   $101.00  
  Purchase #2 $212.87   13.649%   $241.9246   $241.92   $241.90   $241.90  
  Purchase #3 $241.60   6.483%   $257.2629   $257.26   $257.25   $257.30  
  Purchase #4 $230.82   5.226%   $242.8827   $242.88   $242.90   $242.90  
  Purchase #5 $133.58   8.644%   $145.1267   $145.13   $145.15   $145.10  
  Purchase #6 $85.99   4.838%   $90.1502   $90.15   $90.15   $90.20  
  Purchase #7 $83.56   3.690%   $86.6434   $86.64   $86.65   $86.60  
  7 purchase totals = $1,081.36       $1,165.0339   $1,165.02   $1,165.05   $1,165.00