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 $32.57   10.477%   $35.9824   $35.98   $36.00   $36.00  
  Purchase #2 $172.96   11.109%   $192.1741   $192.17   $192.15   $192.20  
  Purchase #3 $168.72   4.540%   $176.3799   $176.38   $176.40   $176.40  
  Purchase #4 $69.62   9.371%   $76.1441   $76.14   $76.15   $76.10  
  Purchase #5 $129.76   11.406%   $144.5604   $144.56   $144.55   $144.60  
  Purchase #6 $150.53   11.603%   $167.996   $168.00   $168.00   $168.00  
  Purchase #7 $207.96   10.870%   $230.5653   $230.57   $230.55   $230.60  
  7 purchase totals = $932.12       $1,023.8022   $1,023.80   $1,023.80   $1,023.90