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 $69.25   6.800%   $73.959   $73.96   $73.95   $74.00  
  Purchase #2 $181.84   5.640%   $192.0958   $192.10   $192.10   $192.10  
  Purchase #3 $81.63   3.807%   $84.7377   $84.74   $84.75   $84.70  
  Purchase #4 $182.60   13.733%   $207.6765   $207.68   $207.70   $207.70  
  Purchase #5 $61.49   10.657%   $68.043   $68.04   $68.05   $68.00  
  Purchase #6 $54.86   12.178%   $61.5409   $61.54   $61.55   $61.50  
  Purchase #7 $225.34   10.787%   $249.6474   $249.65   $249.65   $249.60  
  7 purchase totals = $857.01       $937.7003   $937.71   $937.75   $937.60