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 $55.61   11.630%   $62.0774   $62.08   $62.10   $62.10  
  Purchase #2 $187.40   12.604%   $211.0199   $211.02   $211.00   $211.00  
  Purchase #3 $19.92   4.262%   $20.769   $20.77   $20.75   $20.80  
  Purchase #4 $127.90   4.434%   $133.5711   $133.57   $133.55   $133.60  
  Purchase #5 $34.61   8.333%   $37.4941   $37.49   $37.50   $37.50  
  Purchase #6 $210.28   4.859%   $220.4975   $220.50   $220.50   $220.50  
  Purchase #7 $244.91   9.778%   $268.8573   $268.86   $268.85   $268.90  
  7 purchase totals = $880.63       $954.2863   $954.29   $954.25   $954.40