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 $112.98   5.336%   $119.0086   $119.01   $119.00   $119.00  
  Purchase #2 $60.26   6.113%   $63.9437   $63.94   $63.95   $63.90  
  Purchase #3 $170.66   4.585%   $178.4848   $178.48   $178.50   $178.50  
  Purchase #4 $208.71   13.184%   $236.2263   $236.23   $236.25   $236.20  
  Purchase #5 $152.32   6.191%   $161.7501   $161.75   $161.75   $161.80  
  Purchase #6 $212.45   5.399%   $223.9202   $223.92   $223.90   $223.90  
  Purchase #7 $169.92   5.817%   $179.8042   $179.80   $179.80   $179.80  
  7 purchase totals = $1,087.30       $1,163.1379   $1,163.13   $1,163.15   $1,163.10