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 $201.80   6.145%   $214.2006   $214.20   $214.20   $214.20  
  Purchase #2 $164.37   10.516%   $181.6551   $181.66   $181.65   $181.70  
  Purchase #3 $21.48   11.853%   $24.026   $24.03   $24.05   $24.00  
  Purchase #4 $223.69   3.135%   $230.7027   $230.70   $230.70   $230.70  
  Purchase #5 $193.52   9.559%   $212.0186   $212.02   $212.00   $212.00  
  Purchase #6 $114.73   10.622%   $126.9166   $126.92   $126.90   $126.90  
  Purchase #7 $201.42   5.217%   $211.9281   $211.93   $211.95   $211.90  
  7 purchase totals = $1,121.01       $1,201.4477   $1,201.46   $1,201.45   $1,201.40