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	$105.63	5.246%	$111.1713	$111.17	$111.15	$111.20
Purchase #2	$46.36	6.376%	$49.3159	$49.32	$49.30	$49.30
Purchase #3	$138.87	9.364%	$151.8738	$151.87	$151.85	$151.90
Purchase #4	$207.33	10.771%	$229.6615	$229.66	$229.65	$229.70
Purchase #5	$227.43	4.650%	$238.0055	$238.01	$238.00	$238.00
Purchase #6	$206.61	7.866%	$222.8619	$222.86	$222.85	$222.90
Purchase #7	$129.55	11.696%	$144.7022	$144.70	$144.70	$144.70
7 purchase totals =	$1,061.78		$1,147.5921	$1,147.59	$1,147.50	$1,147.70