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 $98.59   4.120%   $102.6519   $102.65   $102.65   $102.70  
  Purchase #2 $168.55   8.631%   $183.0976   $183.10   $183.10   $183.10  
  Purchase #3 $198.64   6.223%   $211.0014   $211.00   $211.00   $211.00  
  Purchase #4 $93.35   5.802%   $98.7662   $98.77   $98.75   $98.80  
  Purchase #5 $190.63   12.267%   $214.0146   $214.01   $214.00   $214.00  
  Purchase #6 $173.48   7.730%   $186.89   $186.89   $186.90   $186.90  
  Purchase #7 $62.43   6.167%   $66.2801   $66.28   $66.30   $66.30  
  7 purchase totals = $985.67       $1,062.7018   $1,062.70   $1,062.70   $1,062.80