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	$43.91	4.719%	$45.9821	$45.98	$46.00	$46.00
Purchase #2	$50.78	3.420%	$52.5167	$52.52	$52.50	$52.50
Purchase #3	$106.61	4.342%	$111.239	$111.24	$111.25	$111.20
Purchase #4	$212.78	9.750%	$233.5261	$233.53	$233.55	$233.50
Purchase #5	$153.54	11.382%	$171.0159	$171.02	$171.00	$171.00
Purchase #6	$55.43	4.262%	$57.7924	$57.79	$57.80	$57.80
Purchase #7	$65.76	11.720%	$73.4671	$73.47	$73.45	$73.50
7 purchase totals =	$688.81		$745.5393	$745.55	$745.55	$745.50