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	$102.35	10.128%	$112.716	$112.72	$112.70	$112.70
Purchase #2	$87.58	4.738%	$91.7295	$91.73	$91.75	$91.70
Purchase #3	$210.56	6.257%	$223.7347	$223.73	$223.75	$223.70
Purchase #4	$104.78	6.858%	$111.9658	$111.97	$111.95	$112.00
Purchase #5	$90.64	9.728%	$99.4575	$99.46	$99.45	$99.50
Purchase #6	$217.93	5.589%	$230.1101	$230.11	$230.10	$230.10
Purchase #7	$113.59	4.144%	$118.2972	$118.30	$118.30	$118.30
7 purchase totals =	$927.43		$988.0108	$988.02	$988.00	$988.00