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 $162.87   13.553%   $184.9438   $184.94   $184.95   $184.90  
  Purchase #2 $186.83   6.819%   $199.5699   $199.57   $199.55   $199.60  
  Purchase #3 $197.61   4.719%   $206.9352   $206.94   $206.95   $206.90  
  Purchase #4 $80.74   9.505%   $88.4143   $88.41   $88.40   $88.40  
  Purchase #5 $156.96   7.371%   $168.5295   $168.53   $168.55   $168.50  
  Purchase #6 $147.34   8.600%   $160.0112   $160.01   $160.00   $160.00  
  Purchase #7 $43.32   8.656%   $47.0698   $47.07   $47.05   $47.10  
  7 purchase totals = $975.67       $1,055.4737   $1,055.47   $1,055.45   $1,055.40