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 $186.93   4.403%   $195.1605   $195.16   $195.15   $195.20  
  Purchase #2 $230.43   5.695%   $243.553   $243.55   $243.55   $243.60  
  Purchase #3 $250.44   11.217%   $278.5319   $278.53   $278.55   $278.50  
  Purchase #4 $186.76   3.124%   $192.5944   $192.59   $192.60   $192.60  
  Purchase #5 $65.54   13.311%   $74.264   $74.26   $74.25   $74.30  
  Purchase #6 $245.49   5.221%   $258.307   $258.31   $258.30   $258.30  
  Purchase #7 $147.66   9.851%   $162.206   $162.21   $162.20   $162.20  
  7 purchase totals = $1,313.25       $1,404.6168   $1,404.61   $1,404.60   $1,404.70