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 $32.54   11.775%   $36.3716   $36.37   $36.35   $36.40  
  Purchase #2 $174.31   7.702%   $187.7354   $187.74   $187.75   $187.70  
  Purchase #3 $214.61   3.389%   $221.8831   $221.88   $221.90   $221.90  
  Purchase #4 $68.86   9.798%   $75.6069   $75.61   $75.60   $75.60  
  Purchase #5 $125.98   7.538%   $135.4764   $135.48   $135.50   $135.50  
  Purchase #6 $185.83   6.580%   $198.0576   $198.06   $198.05   $198.10  
  Purchase #7 $192.74   4.238%   $200.9083   $200.91   $200.90   $200.90  
  7 purchase totals = $994.87       $1,056.0393   $1,056.05   $1,056.05   $1,056.10