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 $176.52   4.322%   $184.1492   $184.15   $184.15   $184.10  
  Purchase #2 $83.55   5.305%   $87.9823   $87.98   $88.00   $88.00  
  Purchase #3 $168.45   4.494%   $176.0201   $176.02   $176.00   $176.00  
  Purchase #4 $100.94   4.264%   $105.2441   $105.24   $105.25   $105.20  
  Purchase #5 $26.49   11.783%   $29.6113   $29.61   $29.60   $29.60  
  Purchase #6 $114.41   10.533%   $126.4608   $126.46   $126.45   $126.50  
  Purchase #7 $140.71   7.323%   $151.0142   $151.01   $151.00   $151.00  
  7 purchase totals = $811.07       $860.4820   $860.47   $860.45   $860.40