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	$113.87	12.660%	$128.2859	$128.29	$128.30	$128.30
Purchase #2	$83.50	7.278%	$89.5771	$89.58	$89.60	$89.60
Purchase #3	$11.91	3.366%	$12.3109	$12.31	$12.30	$12.30
Purchase #4	$230.83	13.395%	$261.7497	$261.75	$261.75	$261.70
Purchase #5	$218.80	4.550%	$228.7554	$228.76	$228.75	$228.80
Purchase #6	$79.66	8.271%	$86.2487	$86.25	$86.25	$86.20
Purchase #7	$230.31	4.548%	$240.7845	$240.78	$240.80	$240.80
7 purchase totals =	$968.88		$1,047.7122	$1,047.72	$1,047.75	$1,047.70