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 $158.90   11.295%   $176.8478   $176.85   $176.85   $176.80  
  Purchase #2 $223.32   4.754%   $233.9366   $233.94   $233.95   $233.90  
  Purchase #3 $52.66   7.310%   $56.5094   $56.51   $56.50   $56.50  
  Purchase #4 $199.25   11.171%   $221.5082   $221.51   $221.50   $221.50  
  Purchase #5 $186.46   7.687%   $200.7932   $200.79   $200.80   $200.80  
  Purchase #6 $183.25   9.747%   $201.1114   $201.11   $201.10   $201.10  
  Purchase #7 $79.99   7.596%   $86.066   $86.07   $86.05   $86.10  
  7 purchase totals = $1,083.83       $1,176.7726   $1,176.78   $1,176.75   $1,176.70