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 $104.89   10.627%   $116.0367   $116.04   $116.05   $116.00  
  Purchase #2 $232.75   5.239%   $244.9438   $244.94   $244.95   $244.90  
  Purchase #3 $192.44   13.215%   $217.8709   $217.87   $217.85   $217.90  
  Purchase #4 $6.77   12.349%   $7.606   $7.61   $7.60   $7.60  
  Purchase #5 $96.57   5.397%   $101.7819   $101.78   $101.80   $101.80  
  Purchase #6 $82.85   8.793%   $90.135   $90.14   $90.15   $90.10  
  Purchase #7 $93.44   3.678%   $96.8767   $96.88   $96.90   $96.90  
  7 purchase totals = $809.71       $875.2510   $875.26   $875.30   $875.20