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 $41.54   6.792%   $44.3614   $44.36   $44.35   $44.40  
  Purchase #2 $125.99   5.460%   $132.8691   $132.87   $132.85   $132.90  
  Purchase #3 $24.73   5.237%   $26.0251   $26.03   $26.05   $26.00  
  Purchase #4 $183.74   9.779%   $201.7079   $201.71   $201.70   $201.70  
  Purchase #5 $120.73   7.194%   $129.4153   $129.42   $129.40   $129.40  
  Purchase #6 $167.27   11.143%   $185.9089   $185.91   $185.90   $185.90  
  Purchase #7 $237.33   4.546%   $248.119   $248.12   $248.10   $248.10  
  7 purchase totals = $901.33       $968.4067   $968.42   $968.35   $968.40