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 $208.33   4.784%   $218.2965   $218.30   $218.30   $218.30  
  Purchase #2 $57.95   13.290%   $65.6516   $65.65   $65.65   $65.70  
  Purchase #3 $106.33   6.851%   $113.6147   $113.61   $113.60   $113.60  
  Purchase #4 $17.84   7.319%   $19.1457   $19.15   $19.15   $19.10  
  Purchase #5 $163.41   4.604%   $170.9334   $170.93   $170.95   $170.90  
  Purchase #6 $95.44   12.616%   $107.4807   $107.48   $107.50   $107.50  
  Purchase #7 $235.83   13.324%   $267.252   $267.25   $267.25   $267.30  
  7 purchase totals = $885.13       $962.3746   $962.37   $962.40   $962.40