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 $71.82   7.167%   $76.9673   $76.97   $76.95   $77.00  
  Purchase #2 $148.81   4.863%   $156.0466   $156.05   $156.05   $156.00  
  Purchase #3 $112.95   5.549%   $119.2176   $119.22   $119.20   $119.20  
  Purchase #4 $128.37   4.535%   $134.1916   $134.19   $134.20   $134.20  
  Purchase #5 $91.91   4.874%   $96.3897   $96.39   $96.40   $96.40  
  Purchase #6 $205.95   12.654%   $232.0109   $232.01   $232.00   $232.00  
  Purchase #7 $58.39   3.468%   $60.415   $60.42   $60.40   $60.40  
  7 purchase totals = $818.20       $875.2387   $875.25   $875.20   $875.20