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	$114.29	3.259%	$118.0147	$118.01	$118.00	$118.00
Purchase #2	$231.91	8.267%	$251.082	$251.08	$251.10	$251.10
Purchase #3	$136.32	7.139%	$146.0519	$146.05	$146.05	$146.10
Purchase #4	$246.36	7.395%	$264.5783	$264.58	$264.60	$264.60
Purchase #5	$116.76	9.758%	$128.1534	$128.15	$128.15	$128.20
Purchase #6	$95.58	12.389%	$107.4214	$107.42	$107.40	$107.40
Purchase #7	$114.31	11.647%	$127.6237	$127.62	$127.60	$127.60
7 purchase totals =	$1,055.53		$1,142.9254	$1,142.91	$1,142.90	$1,143.00