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 $165.98   5.652%   $175.3612   $175.36   $175.35   $175.40  
  Purchase #2 $114.32   9.656%   $125.3587   $125.36   $125.35   $125.40  
  Purchase #3 $42.57   8.613%   $46.2366   $46.24   $46.25   $46.20  
  Purchase #4 $216.65   10.606%   $239.6279   $239.63   $239.65   $239.60  
  Purchase #5 $75.60   3.185%   $78.0079   $78.01   $78.00   $78.00  
  Purchase #6 $107.32   13.601%   $121.9166   $121.92   $121.90   $121.90  
  Purchase #7 $141.54   4.222%   $147.5158   $147.52   $147.50   $147.50  
  7 purchase totals = $863.98       $934.0247   $934.04   $934.00   $934.00