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	$155.62	6.519%	$165.7649	$165.76	$165.75	$165.80
Purchase #2	$165.26	4.509%	$172.7116	$172.71	$172.70	$172.70
Purchase #3	$99.82	11.810%	$111.6087	$111.61	$111.60	$111.60
Purchase #4	$220.25	7.273%	$236.2688	$236.27	$236.25	$236.30
Purchase #5	$184.96	7.247%	$198.3641	$198.36	$198.35	$198.40
Purchase #6	$213.56	4.549%	$223.2748	$223.27	$223.25	$223.30
Purchase #7	$11.66	10.382%	$12.8705	$12.87	$12.85	$12.90
7 purchase totals =	$1,051.13		$1,120.8634	$1,120.85	$1,120.75	$1,121.00