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 $119.30   6.202%   $126.699   $126.70   $126.70   $126.70  
  Purchase #2 $193.71   13.667%   $220.1843   $220.18   $220.20   $220.20  
  Purchase #3 $45.68   10.518%   $50.4846   $50.48   $50.50   $50.50  
  Purchase #4 $82.93   5.849%   $87.7806   $87.78   $87.80   $87.80  
  Purchase #5 $198.99   4.361%   $207.668   $207.67   $207.65   $207.70  
  Purchase #6 $63.54   9.500%   $69.5763   $69.58   $69.60   $69.60  
  Purchase #7 $165.50   3.415%   $171.1518   $171.15   $171.15   $171.20  
  7 purchase totals = $869.65       $933.5446   $933.54   $933.60   $933.70