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 $54.79   8.771%   $59.5956   $59.60   $59.60   $59.60  
  Purchase #2 $75.71   12.241%   $84.9777   $84.98   $85.00   $85.00  
  Purchase #3 $131.99   13.334%   $149.5895   $149.59   $149.60   $149.60  
  Purchase #4 $208.51   3.612%   $216.0414   $216.04   $216.05   $216.00  
  Purchase #5 $151.89   8.404%   $164.6548   $164.65   $164.65   $164.70  
  Purchase #6 $203.97   6.680%   $217.5952   $217.60   $217.60   $217.60  
  Purchase #7 $216.25   10.783%   $239.5682   $239.57   $239.55   $239.60  
  7 purchase totals = $1,043.11       $1,132.0224   $1,132.03   $1,132.05   $1,132.10