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 $172.43   12.551%   $194.0717   $194.07   $194.05   $194.10  
  Purchase #2 $38.74   13.539%   $43.985   $43.99   $44.00   $44.00  
  Purchase #3 $161.28   10.680%   $178.5047   $178.50   $178.50   $178.50  
  Purchase #4 $64.83   12.715%   $73.0731   $73.07   $73.05   $73.10  
  Purchase #5 $58.64   3.866%   $60.907   $60.91   $60.90   $60.90  
  Purchase #6 $235.73   7.851%   $254.2372   $254.24   $254.25   $254.20  
  Purchase #7 $218.70   11.111%   $242.9998   $243.00   $243.00   $243.00  
  7 purchase totals = $950.35       $1,047.7785   $1,047.78   $1,047.75   $1,047.80