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	$41.41	5.122%	$43.531	$43.53	$43.55	$43.50
Purchase #2	$136.88	3.834%	$142.128	$142.13	$142.15	$142.10
Purchase #3	$215.41	10.660%	$238.3727	$238.37	$238.35	$238.40
Purchase #4	$30.46	12.271%	$34.1977	$34.20	$34.20	$34.20
Purchase #5	$250.31	4.212%	$260.8531	$260.85	$260.85	$260.90
Purchase #6	$182.90	6.222%	$194.28	$194.28	$194.30	$194.30
Purchase #7	$85.88	5.671%	$90.7503	$90.75	$90.75	$90.80
7 purchase totals =	$943.25		$1,004.1128	$1,004.11	$1,004.15	$1,004.20