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 $34.31   5.621%   $36.2386   $36.24   $36.25   $36.20  
  Purchase #2 $246.46   11.165%   $273.9773   $273.98   $274.00   $274.00  
  Purchase #3 $97.33   6.526%   $103.6818   $103.68   $103.70   $103.70  
  Purchase #4 $108.64   6.352%   $115.5408   $115.54   $115.55   $115.50  
  Purchase #5 $207.29   3.597%   $214.7462   $214.75   $214.75   $214.70  
  Purchase #6 $206.49   10.258%   $227.6717   $227.67   $227.65   $227.70  
  Purchase #7 $92.86   11.869%   $103.8816   $103.88   $103.90   $103.90  
  7 purchase totals = $993.38       $1,075.7380   $1,075.74   $1,075.80   $1,075.70