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 $226.34   8.818%   $246.2987   $246.30   $246.30   $246.30  
  Purchase #2 $208.93   4.714%   $218.779   $218.78   $218.80   $218.80  
  Purchase #3 $41.51   3.708%   $43.0492   $43.05   $43.05   $43.00  
  Purchase #4 $68.53   5.762%   $72.4787   $72.48   $72.50   $72.50  
  Purchase #5 $168.89   8.529%   $183.2946   $183.29   $183.30   $183.30  
  Purchase #6 $168.35   4.707%   $176.2742   $176.27   $176.25   $176.30  
  Purchase #7 $224.49   13.822%   $255.519   $255.52   $255.50   $255.50  
  7 purchase totals = $1,107.04       $1,195.6934   $1,195.69   $1,195.70   $1,195.70