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 $205.55   5.227%   $216.2941   $216.29   $216.30   $216.30  
  Purchase #2 $151.87   9.522%   $166.3311   $166.33   $166.35   $166.30  
  Purchase #3 $206.51   8.750%   $224.5796   $224.58   $224.60   $224.60  
  Purchase #4 $32.71   5.512%   $34.513   $34.51   $34.50   $34.50  
  Purchase #5 $222.99   8.212%   $241.3019   $241.30   $241.30   $241.30  
  Purchase #6 $212.63   3.325%   $219.6999   $219.70   $219.70   $219.70  
  Purchase #7 $230.30   6.208%   $244.597   $244.60   $244.60   $244.60  
  7 purchase totals = $1,262.56       $1,347.3166   $1,347.31   $1,347.35   $1,347.30