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 $187.75   11.209%   $208.7949   $208.79   $208.80   $208.80  
  Purchase #2 $218.81   12.863%   $246.9555   $246.96   $246.95   $247.00  
  Purchase #3 $215.59   13.400%   $244.4791   $244.48   $244.50   $244.50  
  Purchase #4 $145.92   6.445%   $155.3245   $155.32   $155.30   $155.30  
  Purchase #5 $191.67   12.128%   $214.9157   $214.92   $214.90   $214.90  
  Purchase #6 $186.87   11.176%   $207.7546   $207.75   $207.75   $207.80  
  Purchase #7 $176.47   7.161%   $189.107   $189.11   $189.10   $189.10  
  7 purchase totals = $1,323.08       $1,467.3313   $1,467.33   $1,467.30   $1,467.40