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 $55.38   7.620%   $59.6   $59.60   $59.60   $59.60  
  Purchase #2 $184.94   12.306%   $207.6987   $207.70   $207.70   $207.70  
  Purchase #3 $86.78   10.608%   $95.9856   $95.99   $96.00   $96.00  
  Purchase #4 $228.92   9.367%   $250.3629   $250.36   $250.35   $250.40  
  Purchase #5 $68.73   3.309%   $71.0043   $71.00   $71.00   $71.00  
  Purchase #6 $219.73   8.836%   $239.1453   $239.15   $239.15   $239.10  
  Purchase #7 $116.55   13.697%   $132.5139   $132.51   $132.50   $132.50  
  7 purchase totals = $961.03       $1,056.3107   $1,056.31   $1,056.30   $1,056.30