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 $59.48   5.822%   $62.9429   $62.94   $62.95   $62.90  
  Purchase #2 $183.95   6.577%   $196.0484   $196.05   $196.05   $196.00  
  Purchase #3 $215.25   11.192%   $239.3408   $239.34   $239.35   $239.30  
  Purchase #4 $110.44   7.534%   $118.7605   $118.76   $118.75   $118.80  
  Purchase #5 $214.85   6.345%   $228.4822   $228.48   $228.50   $228.50  
  Purchase #6 $129.81   13.717%   $147.616   $147.62   $147.60   $147.60  
  Purchase #7 $11.73   13.568%   $13.3215   $13.32   $13.30   $13.30  
  7 purchase totals = $925.51       $1,006.5123   $1,006.51   $1,006.50   $1,006.40