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 $86.40   10.293%   $95.2932   $95.29   $95.30   $95.30  
  Purchase #2 $241.97   4.738%   $253.4345   $253.43   $253.45   $253.40  
  Purchase #3 $143.55   13.752%   $163.291   $163.29   $163.30   $163.30  
  Purchase #4 $165.76   4.680%   $173.5176   $173.52   $173.50   $173.50  
  Purchase #5 $212.92   7.857%   $229.6491   $229.65   $229.65   $229.60  
  Purchase #6 $157.98   13.243%   $178.9013   $178.90   $178.90   $178.90  
  Purchase #7 $196.86   8.572%   $213.7348   $213.73   $213.75   $213.70  
  7 purchase totals = $1,205.44       $1,307.8215   $1,307.81   $1,307.85   $1,307.70