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	$243.79	4.527%	$254.8264	$254.83	$254.85	$254.80
Purchase #2	$65.92	8.596%	$71.5865	$71.59	$71.60	$71.60
Purchase #3	$35.61	13.267%	$40.3344	$40.33	$40.35	$40.30
Purchase #4	$106.29	12.333%	$119.3987	$119.40	$119.40	$119.40
Purchase #5	$241.51	10.530%	$266.941	$266.94	$266.95	$266.90
Purchase #6	$244.27	9.185%	$266.7062	$266.71	$266.70	$266.70
Purchase #7	$114.70	11.359%	$127.7288	$127.73	$127.75	$127.70
7 purchase totals =	$1,052.09		$1,147.5220	$1,147.53	$1,147.60	$1,147.40