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 $183.81   8.368%   $199.1912   $199.19   $199.20   $199.20  
  Purchase #2 $202.43   7.677%   $217.9706   $217.97   $217.95   $218.00  
  Purchase #3 $65.53   5.421%   $69.0824   $69.08   $69.10   $69.10  
  Purchase #4 $124.93   4.482%   $130.5294   $130.53   $130.55   $130.50  
  Purchase #5 $40.60   7.623%   $43.6949   $43.69   $43.70   $43.70  
  Purchase #6 $217.87   5.510%   $229.8746   $229.87   $229.85   $229.90  
  Purchase #7 $157.63   3.623%   $163.3409   $163.34   $163.35   $163.30  
  7 purchase totals = $992.80       $1,053.6840   $1,053.67   $1,053.70   $1,053.70