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 $101.36   4.838%   $106.2638   $106.26   $106.25   $106.30  
  Purchase #2 $131.44   7.527%   $141.3335   $141.33   $141.35   $141.30  
  Purchase #3 $66.78   4.243%   $69.6135   $69.61   $69.60   $69.60  
  Purchase #4 $63.77   6.832%   $68.1268   $68.13   $68.15   $68.10  
  Purchase #5 $64.52   10.627%   $71.3765   $71.38   $71.40   $71.40  
  Purchase #6 $217.50   7.325%   $233.4319   $233.43   $233.45   $233.40  
  Purchase #7 $59.57   11.247%   $66.2698   $66.27   $66.25   $66.30  
  7 purchase totals = $704.94       $756.4158   $756.41   $756.45   $756.40