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 $105.31   13.711%   $119.7491   $119.75   $119.75   $119.70  
  Purchase #2 $102.41   8.120%   $110.7257   $110.73   $110.75   $110.70  
  Purchase #3 $198.95   7.566%   $214.0026   $214.00   $214.00   $214.00  
  Purchase #4 $166.86   10.557%   $184.4754   $184.48   $184.50   $184.50  
  Purchase #5 $153.70   5.488%   $162.1351   $162.14   $162.15   $162.10  
  Purchase #6 $151.28   5.741%   $159.965   $159.97   $159.95   $160.00  
  Purchase #7 $189.65   3.644%   $196.5608   $196.56   $196.55   $196.60  
  7 purchase totals = $1,068.16       $1,147.6137   $1,147.63   $1,147.65   $1,147.60