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 $86.65   9.105%   $94.5395   $94.54   $94.55   $94.50  
  Purchase #2 $187.75   9.426%   $205.4473   $205.45   $205.45   $205.40  
  Purchase #3 $155.35   3.613%   $160.9628   $160.96   $160.95   $161.00  
  Purchase #4 $179.57   3.502%   $185.8585   $185.86   $185.85   $185.90  
  Purchase #5 $232.55   7.190%   $249.2703   $249.27   $249.25   $249.30  
  Purchase #6 $132.71   6.683%   $141.579   $141.58   $141.60   $141.60  
  Purchase #7 $10.66   12.670%   $12.0106   $12.01   $12.00   $12.00  
  7 purchase totals = $985.24       $1,049.6680   $1,049.67   $1,049.65   $1,049.70