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	$51.65	6.730%	$55.126	$55.13	$55.15	$55.10
Purchase #2	$136.51	5.802%	$144.4303	$144.43	$144.45	$144.40
Purchase #3	$206.93	6.718%	$220.8316	$220.83	$220.85	$220.80
Purchase #4	$206.25	8.350%	$223.4719	$223.47	$223.45	$223.50
Purchase #5	$169.66	12.849%	$191.4596	$191.46	$191.45	$191.50
Purchase #6	$46.38	4.621%	$48.5232	$48.52	$48.50	$48.50
Purchase #7	$172.29	3.583%	$178.4632	$178.46	$178.45	$178.50
7 purchase totals =	$989.67		$1,062.3058	$1,062.30	$1,062.30	$1,062.30