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	$229.30	3.439%	$237.1856	$237.19	$237.20	$237.20
Purchase #2	$231.54	4.637%	$242.2765	$242.28	$242.30	$242.30
Purchase #3	$52.45	7.344%	$56.3019	$56.30	$56.30	$56.30
Purchase #4	$50.96	12.106%	$57.1292	$57.13	$57.15	$57.10
Purchase #5	$131.74	7.816%	$142.0368	$142.04	$142.05	$142.00
Purchase #6	$108.48	9.491%	$118.7758	$118.78	$118.80	$118.80
Purchase #7	$136.25	9.169%	$148.7428	$148.74	$148.75	$148.70
7 purchase totals =	$940.72		$1,002.4486	$1,002.46	$1,002.55	$1,002.40