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 $88.33   8.841%   $96.1393   $96.14   $96.15   $96.10  
  Purchase #2 $92.58   3.650%   $95.9592   $95.96   $95.95   $96.00  
  Purchase #3 $202.32   11.164%   $224.907   $224.91   $224.90   $224.90  
  Purchase #4 $159.81   12.796%   $180.2593   $180.26   $180.25   $180.30  
  Purchase #5 $52.53   9.295%   $57.4127   $57.41   $57.40   $57.40  
  Purchase #6 $219.76   8.271%   $237.9363   $237.94   $237.95   $237.90  
  Purchase #7 $179.79   7.118%   $192.5875   $192.59   $192.60   $192.60  
  7 purchase totals = $995.12       $1,085.2013   $1,085.21   $1,085.20   $1,085.20