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 $85.25   13.455%   $96.7204   $96.72   $96.70   $96.70  
  Purchase #2 $212.87   10.415%   $235.0404   $235.04   $235.05   $235.00  
  Purchase #3 $238.53   6.234%   $253.4   $253.40   $253.40   $253.40  
  Purchase #4 $240.34   10.575%   $265.756   $265.76   $265.75   $265.80  
  Purchase #5 $96.67   5.116%   $101.6156   $101.62   $101.60   $101.60  
  Purchase #6 $101.32   6.121%   $107.5218   $107.52   $107.50   $107.50  
  Purchase #7 $90.93   3.274%   $93.907   $93.91   $93.90   $93.90  
  7 purchase totals = $1,065.91       $1,153.9612   $1,153.97   $1,153.90   $1,153.90