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 $70.25   5.369%   $74.0217   $74.02   $74.00   $74.00  
  Purchase #2 $11.41   10.463%   $12.6038   $12.60   $12.60   $12.60  
  Purchase #3 $214.72   3.259%   $221.7177   $221.72   $221.70   $221.70  
  Purchase #4 $171.27   6.689%   $182.7263   $182.73   $182.75   $182.70  
  Purchase #5 $9.25   11.451%   $10.3092   $10.31   $10.30   $10.30  
  Purchase #6 $242.89   8.446%   $263.4045   $263.40   $263.40   $263.40  
  Purchase #7 $249.49   7.769%   $268.8729   $268.87   $268.85   $268.90  
  7 purchase totals = $969.28       $1,033.6561   $1,033.65   $1,033.60   $1,033.60