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	$73.60	5.628%	$77.7422	$77.74	$77.75	$77.70
Purchase #2	$111.89	7.675%	$120.4776	$120.48	$120.50	$120.50
Purchase #3	$226.96	13.114%	$256.7235	$256.72	$256.70	$256.70
Purchase #4	$154.52	8.638%	$167.8674	$167.87	$167.85	$167.90
Purchase #5	$99.79	3.110%	$102.8935	$102.89	$102.90	$102.90
Purchase #6	$106.37	4.686%	$111.3545	$111.35	$111.35	$111.40
Purchase #7	$184.62	4.566%	$193.0497	$193.05	$193.05	$193.00
7 purchase totals =	$957.75		$1,030.1084	$1,030.10	$1,030.10	$1,030.10