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	$111.53	7.147%	$119.501	$119.50	$119.50	$119.50
Purchase #2	$105.73	4.545%	$110.5354	$110.54	$110.55	$110.50
Purchase #3	$245.64	4.108%	$255.7309	$255.73	$255.75	$255.70
Purchase #4	$143.73	7.478%	$154.4781	$154.48	$154.50	$154.50
Purchase #5	$170.67	7.457%	$183.3969	$183.40	$183.40	$183.40
Purchase #6	$105.52	13.603%	$119.8739	$119.87	$119.85	$119.90
Purchase #7	$204.76	6.114%	$217.279	$217.28	$217.30	$217.30
7 purchase totals =	$1,087.58		$1,160.7952	$1,160.80	$1,160.85	$1,160.80