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 $202.35   4.535%   $211.5266   $211.53   $211.55   $211.50  
  Purchase #2 $21.43   12.695%   $24.1505   $24.15   $24.15   $24.20  
  Purchase #3 $242.63   3.873%   $252.0271   $252.03   $252.05   $252.00  
  Purchase #4 $102.80   5.313%   $108.2618   $108.26   $108.25   $108.30  
  Purchase #5 $214.27   13.458%   $243.1065   $243.11   $243.10   $243.10  
  Purchase #6 $241.64   4.374%   $252.2093   $252.21   $252.20   $252.20  
  Purchase #7 $246.25   11.148%   $273.702   $273.70   $273.70   $273.70  
  7 purchase totals = $1,271.37       $1,364.9838   $1,364.99   $1,365.00   $1,365.00