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 $57.36   5.166%   $60.3232   $60.32   $60.30   $60.30  
  Purchase #2 $208.31   4.107%   $216.8653   $216.87   $216.85   $216.90  
  Purchase #3 $52.50   7.162%   $56.2601   $56.26   $56.25   $56.30  
  Purchase #4 $238.78   11.712%   $266.7459   $266.75   $266.75   $266.70  
  Purchase #5 $36.99   7.642%   $39.8168   $39.82   $39.80   $39.80  
  Purchase #6 $128.33   4.693%   $134.3525   $134.35   $134.35   $134.40  
  Purchase #7 $85.94   8.670%   $93.391   $93.39   $93.40   $93.40  
  7 purchase totals = $808.21       $867.7548   $867.76   $867.70   $867.80