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	$226.32	10.788%	$250.7354	$250.74	$250.75	$250.70
Purchase #2	$158.91	9.761%	$174.4212	$174.42	$174.40	$174.40
Purchase #3	$178.31	4.409%	$186.1717	$186.17	$186.15	$186.20
Purchase #4	$62.80	4.351%	$65.5324	$65.53	$65.55	$65.50
Purchase #5	$135.86	13.412%	$154.0815	$154.08	$154.10	$154.10
Purchase #6	$56.60	4.751%	$59.2891	$59.29	$59.30	$59.30
Purchase #7	$233.48	11.388%	$260.0687	$260.07	$260.05	$260.10
7 purchase totals =	$1,052.28		$1,150.3000	$1,150.30	$1,150.30	$1,150.30