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	$106.63	4.548%	$111.4795	$111.48	$111.50	$111.50
Purchase #2	$120.73	10.706%	$133.6554	$133.66	$133.65	$133.70
Purchase #3	$226.94	4.388%	$236.8981	$236.90	$236.90	$236.90
Purchase #4	$46.79	6.464%	$49.8145	$49.81	$49.80	$49.80
Purchase #5	$163.72	12.581%	$184.3176	$184.32	$184.30	$184.30
Purchase #6	$105.29	12.640%	$118.5987	$118.60	$118.60	$118.60
Purchase #7	$37.32	9.385%	$40.8225	$40.82	$40.80	$40.80
7 purchase totals =	$807.42		$875.5863	$875.59	$875.55	$875.60