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 $93.84   4.448%   $98.014   $98.01   $98.00   $98.00  
  Purchase #2 $43.69   5.119%   $45.9265   $45.93   $45.95   $45.90  
  Purchase #3 $58.54   3.267%   $60.4525   $60.45   $60.45   $60.50  
  Purchase #4 $205.64   10.230%   $226.677   $226.68   $226.70   $226.70  
  Purchase #5 $7.49   12.410%   $8.4195   $8.42   $8.40   $8.40  
  Purchase #6 $180.96   9.137%   $197.4943   $197.49   $197.50   $197.50  
  Purchase #7 $188.88   5.153%   $198.613   $198.61   $198.60   $198.60  
  7 purchase totals = $779.04       $835.5968   $835.59   $835.60   $835.60