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 $47.94   10.232%   $52.8452   $52.85   $52.85   $52.80  
  Purchase #2 $212.34   5.251%   $223.49   $223.49   $223.50   $223.50  
  Purchase #3 $226.94   5.552%   $239.5397   $239.54   $239.55   $239.50  
  Purchase #4 $217.55   11.462%   $242.4856   $242.49   $242.50   $242.50  
  Purchase #5 $142.42   9.709%   $156.2476   $156.25   $156.25   $156.20  
  Purchase #6 $169.63   11.321%   $188.8338   $188.83   $188.85   $188.80  
  Purchase #7 $54.53   9.500%   $59.7104   $59.71   $59.70   $59.70  
  7 purchase totals = $1,071.35       $1,163.1523   $1,163.16   $1,163.20   $1,163.00