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 $212.26   8.124%   $229.504   $229.50   $229.50   $229.50  
  Purchase #2 $230.82   9.656%   $253.108   $253.11   $253.10   $253.10  
  Purchase #3 $110.89   6.859%   $118.4959   $118.50   $118.50   $118.50  
  Purchase #4 $33.66   5.793%   $35.6099   $35.61   $35.60   $35.60  
  Purchase #5 $206.60   10.388%   $228.0616   $228.06   $228.05   $228.10  
  Purchase #6 $160.28   10.298%   $176.7856   $176.79   $176.80   $176.80  
  Purchase #7 $208.30   9.261%   $227.5907   $227.59   $227.60   $227.60  
  7 purchase totals = $1,162.81       $1,269.1557   $1,269.16   $1,269.15   $1,269.20