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 $70.89   3.224%   $73.1755   $73.18   $73.20   $73.20  
  Purchase #2 $111.52   10.472%   $123.1984   $123.20   $123.20   $123.20  
  Purchase #3 $60.80   6.771%   $64.9168   $64.92   $64.90   $64.90  
  Purchase #4 $234.81   4.848%   $246.1936   $246.19   $246.20   $246.20  
  Purchase #5 $176.42   9.704%   $193.5398   $193.54   $193.55   $193.50  
  Purchase #6 $94.51   3.172%   $97.5079   $97.51   $97.50   $97.50  
  Purchase #7 $80.73   3.537%   $83.5854   $83.59   $83.60   $83.60  
  7 purchase totals = $829.68       $882.1174   $882.13   $882.15   $882.10