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	$132.93	11.606%	$148.3579	$148.36	$148.35	$148.40
Purchase #2	$38.29	3.237%	$39.5294	$39.53	$39.55	$39.50
Purchase #3	$239.57	12.346%	$269.1473	$269.15	$269.15	$269.10
Purchase #4	$103.63	12.477%	$116.5599	$116.56	$116.55	$116.60
Purchase #5	$187.65	6.147%	$199.1848	$199.18	$199.20	$199.20
Purchase #6	$42.57	7.523%	$45.7725	$45.77	$45.75	$45.80
Purchase #7	$240.29	6.485%	$255.8728	$255.87	$255.85	$255.90
7 purchase totals =	$984.93		$1,074.4246	$1,074.42	$1,074.40	$1,074.50