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	$50.68	8.385%	$54.9295	$54.93	$54.95	$54.90
Purchase #2	$28.90	13.696%	$32.8581	$32.86	$32.85	$32.90
Purchase #3	$237.93	6.225%	$252.7411	$252.74	$252.75	$252.70
Purchase #4	$129.38	10.395%	$142.8291	$142.83	$142.85	$142.80
Purchase #5	$201.56	6.475%	$214.611	$214.61	$214.60	$214.60
Purchase #6	$219.86	9.367%	$240.4543	$240.45	$240.45	$240.50
Purchase #7	$157.46	8.505%	$170.852	$170.85	$170.85	$170.90
7 purchase totals =	$1,025.77		$1,109.2751	$1,109.27	$1,109.30	$1,109.30