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	$189.65	5.461%	$200.0068	$200.01	$200.00	$200.00
Purchase #2	$35.64	4.528%	$37.2538	$37.25	$37.25	$37.30
Purchase #3	$202.53	4.573%	$211.7917	$211.79	$211.80	$211.80
Purchase #4	$207.75	10.254%	$229.0527	$229.05	$229.05	$229.10
Purchase #5	$230.39	13.816%	$262.2207	$262.22	$262.20	$262.20
Purchase #6	$92.42	12.293%	$103.7812	$103.78	$103.80	$103.80
Purchase #7	$119.98	13.534%	$136.2181	$136.22	$136.20	$136.20
7 purchase totals =	$1,078.36		$1,180.3250	$1,180.32	$1,180.30	$1,180.40