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	$204.45	5.829%	$216.3674	$216.37	$216.35	$216.40
Purchase #2	$142.80	13.362%	$161.8809	$161.88	$161.90	$161.90
Purchase #3	$100.61	4.835%	$105.4745	$105.47	$105.45	$105.50
Purchase #4	$136.63	6.763%	$145.8703	$145.87	$145.85	$145.90
Purchase #5	$106.28	12.493%	$119.5576	$119.56	$119.55	$119.60
Purchase #6	$238.70	8.140%	$258.1302	$258.13	$258.15	$258.10
Purchase #7	$7.39	4.632%	$7.7323	$7.73	$7.75	$7.70
7 purchase totals =	$936.86		$1,015.0132	$1,015.01	$1,015.00	$1,015.10