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	$107.82	3.569%	$111.6681	$111.67	$111.65	$111.70
Purchase #2	$129.29	11.444%	$144.0859	$144.09	$144.10	$144.10
Purchase #3	$73.68	11.280%	$81.9911	$81.99	$82.00	$82.00
Purchase #4	$162.34	4.621%	$169.8417	$169.84	$169.85	$169.80
Purchase #5	$118.99	7.103%	$127.4419	$127.44	$127.45	$127.40
Purchase #6	$218.89	8.332%	$237.1279	$237.13	$237.15	$237.10
Purchase #7	$157.31	13.345%	$178.303	$178.30	$178.30	$178.30
7 purchase totals =	$968.32		$1,050.4596	$1,050.46	$1,050.50	$1,050.40