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	$101.34	9.660%	$111.1294	$111.13	$111.15	$111.10
Purchase #2	$184.76	7.515%	$198.6447	$198.64	$198.65	$198.60
Purchase #3	$197.74	12.146%	$221.7575	$221.76	$221.75	$221.80
Purchase #4	$77.60	10.459%	$85.7162	$85.72	$85.70	$85.70
Purchase #5	$208.86	4.668%	$218.6096	$218.61	$218.60	$218.60
Purchase #6	$74.42	9.853%	$81.7526	$81.75	$81.75	$81.80
Purchase #7	$227.97	8.748%	$247.9128	$247.91	$247.90	$247.90
7 purchase totals =	$1,072.69		$1,165.5228	$1,165.52	$1,165.50	$1,165.50