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 $176.25   11.373%   $196.2949   $196.29   $196.30   $196.30  
  Purchase #2 $196.84   8.871%   $214.3017   $214.30   $214.30   $214.30  
  Purchase #3 $224.88   13.505%   $255.25   $255.25   $255.25   $255.30  
  Purchase #4 $190.75   5.767%   $201.7506   $201.75   $201.75   $201.80  
  Purchase #5 $121.33   13.223%   $137.3735   $137.37   $137.35   $137.40  
  Purchase #6 $226.62   12.229%   $254.3334   $254.33   $254.35   $254.30  
  Purchase #7 $20.50   10.573%   $22.6675   $22.67   $22.65   $22.70  
  7 purchase totals = $1,157.17       $1,281.9716   $1,281.96   $1,281.95   $1,282.10