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 $240.80   9.699%   $264.1552   $264.16   $264.15   $264.20  
  Purchase #2 $114.38   10.180%   $126.0239   $126.02   $126.00   $126.00  
  Purchase #3 $120.32   7.184%   $128.9638   $128.96   $128.95   $129.00  
  Purchase #4 $168.86   4.426%   $176.3337   $176.33   $176.35   $176.30  
  Purchase #5 $23.75   8.732%   $25.8239   $25.82   $25.80   $25.80  
  Purchase #6 $201.38   3.540%   $208.5089   $208.51   $208.50   $208.50  
  Purchase #7 $159.95   3.192%   $165.0556   $165.06   $165.05   $165.10  
  7 purchase totals = $1,029.44       $1,094.8650   $1,094.86   $1,094.80   $1,094.90