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 $84.32   9.767%   $92.5555   $92.56   $92.55   $92.60  
  Purchase #2 $240.98   10.132%   $265.3961   $265.40   $265.40   $265.40  
  Purchase #3 $222.79   12.106%   $249.761   $249.76   $249.75   $249.80  
  Purchase #4 $158.84   8.540%   $172.4049   $172.40   $172.40   $172.40  
  Purchase #5 $137.64   9.850%   $151.1975   $151.20   $151.20   $151.20  
  Purchase #6 $111.48   9.133%   $121.6615   $121.66   $121.65   $121.70  
  Purchase #7 $239.84   13.866%   $273.0962   $273.10   $273.10   $273.10  
  7 purchase totals = $1,195.89       $1,326.0727   $1,326.08   $1,326.05   $1,326.20