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 $208.67   9.597%   $228.6961   $228.70   $228.70   $228.70  
  Purchase #2 $187.87   4.318%   $195.9822   $195.98   $196.00   $196.00  
  Purchase #3 $184.65   4.558%   $193.0663   $193.07   $193.05   $193.10  
  Purchase #4 $94.83   3.258%   $97.9196   $97.92   $97.90   $97.90  
  Purchase #5 $97.52   11.384%   $108.6217   $108.62   $108.60   $108.60  
  Purchase #6 $95.86   11.458%   $106.8436   $106.84   $106.85   $106.80  
  Purchase #7 $204.49   11.254%   $227.5033   $227.50   $227.50   $227.50  
  7 purchase totals = $1,073.89       $1,158.6328   $1,158.63   $1,158.60   $1,158.60