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 $224.77   7.581%   $241.8098   $241.81   $241.80   $241.80  
  Purchase #2 $78.97   8.607%   $85.7669   $85.77   $85.75   $85.80  
  Purchase #3 $53.98   4.297%   $56.2995   $56.30   $56.30   $56.30  
  Purchase #4 $158.50   3.262%   $163.6703   $163.67   $163.65   $163.70  
  Purchase #5 $90.62   5.556%   $95.6548   $95.65   $95.65   $95.70  
  Purchase #6 $246.68   9.109%   $269.1501   $269.15   $269.15   $269.20  
  Purchase #7 $216.39   7.636%   $232.9135   $232.91   $232.90   $232.90  
  7 purchase totals = $1,069.91       $1,145.2649   $1,145.26   $1,145.20   $1,145.40