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 $72.40   4.627%   $75.7499   $75.75   $75.75   $75.70  
  Purchase #2 $176.83   12.376%   $198.7145   $198.71   $198.70   $198.70  
  Purchase #3 $223.28   4.266%   $232.8051   $232.81   $232.80   $232.80  
  Purchase #4 $241.57   10.486%   $266.901   $266.90   $266.90   $266.90  
  Purchase #5 $175.40   5.565%   $185.161   $185.16   $185.15   $185.20  
  Purchase #6 $94.37   3.304%   $97.488   $97.49   $97.50   $97.50  
  Purchase #7 $92.41   13.394%   $104.7874   $104.79   $104.80   $104.80  
  7 purchase totals = $1,076.26       $1,161.6069   $1,161.61   $1,161.60   $1,161.60