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 $149.51   8.371%   $162.0255   $162.03   $162.05   $162.00  
  Purchase #2 $184.77   6.240%   $196.2996   $196.30   $196.30   $196.30  
  Purchase #3 $70.65   4.463%   $73.8031   $73.80   $73.80   $73.80  
  Purchase #4 $182.27   9.605%   $199.777   $199.78   $199.80   $199.80  
  Purchase #5 $156.33   4.398%   $163.2054   $163.21   $163.20   $163.20  
  Purchase #6 $36.49   3.627%   $37.8135   $37.81   $37.80   $37.80  
  Purchase #7 $120.70   11.354%   $134.4043   $134.40   $134.40   $134.40  
  7 purchase totals = $900.72       $967.3284   $967.33   $967.35   $967.30