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 $81.89   5.549%   $86.4341   $86.43   $86.45   $86.40  
  Purchase #2 $248.37   5.607%   $262.2961   $262.30   $262.30   $262.30  
  Purchase #3 $211.88   3.807%   $219.9463   $219.95   $219.95   $219.90  
  Purchase #4 $235.45   13.543%   $267.337   $267.34   $267.35   $267.30  
  Purchase #5 $192.60   13.817%   $219.2115   $219.21   $219.20   $219.20  
  Purchase #6 $151.55   5.519%   $159.914   $159.91   $159.90   $159.90  
  Purchase #7 $215.68   7.335%   $231.5001   $231.50   $231.50   $231.50  
  7 purchase totals = $1,337.42       $1,446.6391   $1,446.64   $1,446.65   $1,446.50