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 $88.97   8.293%   $96.3483   $96.35   $96.35   $96.30  
  Purchase #2 $220.99   13.238%   $250.2447   $250.24   $250.25   $250.20  
  Purchase #3 $169.47   8.461%   $183.8089   $183.81   $183.80   $183.80  
  Purchase #4 $67.45   4.310%   $70.3571   $70.36   $70.35   $70.40  
  Purchase #5 $115.29   4.487%   $120.4631   $120.46   $120.45   $120.50  
  Purchase #6 $233.82   11.313%   $260.2721   $260.27   $260.25   $260.30  
  Purchase #7 $211.53   7.179%   $226.7157   $226.72   $226.70   $226.70  
  7 purchase totals = $1,107.52       $1,208.2099   $1,208.21   $1,208.15   $1,208.20