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 $62.82   8.634%   $68.2439   $68.24   $68.25   $68.20  
  Purchase #2 $208.71   4.710%   $218.5402   $218.54   $218.55   $218.50  
  Purchase #3 $126.84   7.518%   $136.3758   $136.38   $136.40   $136.40  
  Purchase #4 $207.72   5.123%   $218.3615   $218.36   $218.35   $218.40  
  Purchase #5 $207.59   13.239%   $235.0728   $235.07   $235.05   $235.10  
  Purchase #6 $110.75   4.697%   $115.9519   $115.95   $115.95   $116.00  
  Purchase #7 $184.80   10.829%   $204.812   $204.81   $204.80   $204.80  
  7 purchase totals = $1,109.23       $1,197.3581   $1,197.35   $1,197.35   $1,197.40