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 $214.60   8.390%   $232.6049   $232.60   $232.60   $232.60  
  Purchase #2 $53.81   10.380%   $59.3955   $59.40   $59.40   $59.40  
  Purchase #3 $237.79   4.379%   $248.2028   $248.20   $248.20   $248.20  
  Purchase #4 $211.93   6.692%   $226.1124   $226.11   $226.10   $226.10  
  Purchase #5 $133.78   8.622%   $145.3145   $145.31   $145.30   $145.30  
  Purchase #6 $154.51   8.657%   $167.8859   $167.89   $167.90   $167.90  
  Purchase #7 $115.69   8.557%   $125.5896   $125.59   $125.60   $125.60  
  7 purchase totals = $1,122.11       $1,205.1056   $1,205.10   $1,205.10   $1,205.10