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	$110.73	6.643%	$118.0858	$118.09	$118.10	$118.10
Purchase #2	$36.48	4.438%	$38.099	$38.10	$38.10	$38.10
Purchase #3	$127.30	5.388%	$134.1589	$134.16	$134.15	$134.20
Purchase #4	$249.42	11.714%	$278.6371	$278.64	$278.65	$278.60
Purchase #5	$232.59	3.543%	$240.8307	$240.83	$240.85	$240.80
Purchase #6	$99.80	12.113%	$111.8888	$111.89	$111.90	$111.90
Purchase #7	$46.94	10.285%	$51.7678	$51.77	$51.75	$51.80
7 purchase totals =	$903.26		$973.4681	$973.48	$973.50	$973.50