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	$57.46	9.216%	$62.7555	$62.76	$62.75	$62.80
Purchase #2	$136.28	12.643%	$153.5099	$153.51	$153.50	$153.50
Purchase #3	$78.75	11.659%	$87.9315	$87.93	$87.95	$87.90
Purchase #4	$248.69	7.124%	$266.4067	$266.41	$266.40	$266.40
Purchase #5	$145.89	3.839%	$151.4907	$151.49	$151.50	$151.50
Purchase #6	$214.51	13.675%	$243.8442	$243.84	$243.85	$243.80
Purchase #7	$42.57	7.255%	$45.6585	$45.66	$45.65	$45.70
7 purchase totals =	$924.15		$1,011.5970	$1,011.60	$1,011.60	$1,011.60