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	$243.77	3.795%	$253.0211	$253.02	$253.00	$253.00
Purchase #2	$19.57	8.569%	$21.247	$21.25	$21.25	$21.20
Purchase #3	$69.84	12.789%	$78.7718	$78.77	$78.75	$78.80
Purchase #4	$193.81	13.867%	$220.6856	$220.69	$220.70	$220.70
Purchase #5	$41.60	12.620%	$46.8499	$46.85	$46.85	$46.80
Purchase #6	$101.25	11.264%	$112.6548	$112.65	$112.65	$112.70
Purchase #7	$50.61	9.245%	$55.2889	$55.29	$55.30	$55.30
7 purchase totals =	$720.45		$788.5191	$788.52	$788.50	$788.50