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 $224.67   8.831%   $244.5106   $244.51   $244.50   $244.50  
  Purchase #2 $41.78   6.166%   $44.3562   $44.36   $44.35   $44.40  
  Purchase #3 $246.46   6.310%   $262.0116   $262.01   $262.00   $262.00  
  Purchase #4 $112.61   3.854%   $116.95   $116.95   $116.95   $117.00  
  Purchase #5 $48.72   11.334%   $54.2419   $54.24   $54.25   $54.20  
  Purchase #6 $179.39   4.848%   $188.0868   $188.09   $188.10   $188.10  
  Purchase #7 $189.47   4.647%   $198.2747   $198.27   $198.25   $198.30  
  7 purchase totals = $1,043.10       $1,108.4318   $1,108.43   $1,108.40   $1,108.50