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 $183.41   7.393%   $196.9695   $196.97   $196.95   $197.00  
  Purchase #2 $165.99   8.610%   $180.2817   $180.28   $180.30   $180.30  
  Purchase #3 $142.61   7.305%   $153.0277   $153.03   $153.05   $153.00  
  Purchase #4 $59.60   8.840%   $64.8686   $64.87   $64.85   $64.90  
  Purchase #5 $51.76   4.364%   $54.0188   $54.02   $54.00   $54.00  
  Purchase #6 $207.50   4.394%   $216.6176   $216.62   $216.60   $216.60  
  Purchase #7 $185.64   7.408%   $199.3922   $199.39   $199.40   $199.40  
  7 purchase totals = $996.51       $1,065.1761   $1,065.18   $1,065.15   $1,065.20