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 $72.28   4.467%   $75.5087   $75.51   $75.50   $75.50  
  Purchase #2 $76.87   6.213%   $81.6459   $81.65   $81.65   $81.60  
  Purchase #3 $200.75   12.595%   $226.0345   $226.03   $226.05   $226.00  
  Purchase #4 $221.92   6.368%   $236.0519   $236.05   $236.05   $236.10  
  Purchase #5 $120.40   5.650%   $127.2026   $127.20   $127.20   $127.20  
  Purchase #6 $85.95   12.511%   $96.7032   $96.70   $96.70   $96.70  
  Purchase #7 $247.87   9.482%   $271.373   $271.37   $271.35   $271.40  
  7 purchase totals = $1,026.04       $1,114.5198   $1,114.51   $1,114.50   $1,114.50