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 $182.46   10.253%   $201.1676   $201.17   $201.15   $201.20  
  Purchase #2 $113.54   11.525%   $126.6255   $126.63   $126.65   $126.60  
  Purchase #3 $57.51   11.294%   $64.0052   $64.01   $64.00   $64.00  
  Purchase #4 $243.59   3.809%   $252.8683   $252.87   $252.85   $252.90  
  Purchase #5 $96.91   3.396%   $100.2011   $100.20   $100.20   $100.20  
  Purchase #6 $111.82   5.440%   $117.903   $117.90   $117.90   $117.90  
  Purchase #7 $242.65   7.699%   $261.3316   $261.33   $261.35   $261.30  
  7 purchase totals = $1,048.48       $1,124.1023   $1,124.11   $1,124.10   $1,124.10