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	$62.73	4.312%	$65.4349	$65.43	$65.45	$65.40
Purchase #2	$73.84	13.161%	$83.5581	$83.56	$83.55	$83.60
Purchase #3	$43.75	10.365%	$48.2847	$48.28	$48.30	$48.30
Purchase #4	$206.38	4.337%	$215.3307	$215.33	$215.35	$215.30
Purchase #5	$159.32	13.233%	$180.4028	$180.40	$180.40	$180.40
Purchase #6	$162.51	7.364%	$174.4772	$174.48	$174.50	$174.50
Purchase #7	$226.56	13.274%	$256.6336	$256.63	$256.65	$256.60
7 purchase totals =	$935.09		$1,024.1220	$1,024.11	$1,024.20	$1,024.10