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 $217.35   12.586%   $244.7057   $244.71   $244.70   $244.70  
  Purchase #2 $184.31   13.730%   $209.6158   $209.62   $209.60   $209.60  
  Purchase #3 $59.71   12.194%   $66.991   $66.99   $67.00   $67.00  
  Purchase #4 $219.80   11.594%   $245.2836   $245.28   $245.30   $245.30  
  Purchase #5 $248.80   7.109%   $266.4872   $266.49   $266.50   $266.50  
  Purchase #6 $126.39   6.393%   $134.4701   $134.47   $134.45   $134.50  
  Purchase #7 $174.34   11.607%   $194.5756   $194.58   $194.60   $194.60  
  7 purchase totals = $1,230.70       $1,362.1290   $1,362.14   $1,362.15   $1,362.20