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 $54.97   8.436%   $59.6073   $59.61   $59.60   $59.60  
  Purchase #2 $226.29   8.658%   $245.8822   $245.88   $245.90   $245.90  
  Purchase #3 $139.59   10.513%   $154.2651   $154.27   $154.25   $154.30  
  Purchase #4 $216.26   7.696%   $232.9034   $232.90   $232.90   $232.90  
  Purchase #5 $47.35   12.335%   $53.1906   $53.19   $53.20   $53.20  
  Purchase #6 $212.98   8.586%   $231.2665   $231.27   $231.25   $231.30  
  Purchase #7 $208.45   12.378%   $234.2519   $234.25   $234.25   $234.30  
  7 purchase totals = $1,105.89       $1,211.3670   $1,211.37   $1,211.35   $1,211.50