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	$246.55	3.560%	$255.3272	$255.33	$255.35	$255.30
Purchase #2	$204.31	3.194%	$210.8357	$210.84	$210.85	$210.80
Purchase #3	$18.58	13.745%	$21.1338	$21.13	$21.15	$21.10
Purchase #4	$28.60	7.294%	$30.6861	$30.69	$30.70	$30.70
Purchase #5	$35.98	13.268%	$40.7538	$40.75	$40.75	$40.80
Purchase #6	$89.42	6.667%	$95.3816	$95.38	$95.40	$95.40
Purchase #7	$72.85	13.178%	$82.4502	$82.45	$82.45	$82.50
7 purchase totals =	$696.29		$736.5684	$736.57	$736.65	$736.60