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	$188.27	4.237%	$196.247	$196.25	$196.25	$196.20
Purchase #2	$84.75	12.533%	$95.3717	$95.37	$95.35	$95.40
Purchase #3	$236.55	3.342%	$244.4555	$244.46	$244.45	$244.50
Purchase #4	$69.88	11.874%	$78.1776	$78.18	$78.20	$78.20
Purchase #5	$203.84	5.543%	$215.1389	$215.14	$215.15	$215.10
Purchase #6	$109.52	6.732%	$116.8929	$116.89	$116.90	$116.90
Purchase #7	$174.51	9.250%	$190.6522	$190.65	$190.65	$190.70
7 purchase totals =	$1,067.32		$1,136.9358	$1,136.94	$1,136.95	$1,137.00