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	$166.52	3.121%	$171.7171	$171.72	$171.70	$171.70
Purchase #2	$18.68	13.822%	$21.2619	$21.26	$21.25	$21.30
Purchase #3	$81.64	11.217%	$90.7976	$90.80	$90.80	$90.80
Purchase #4	$161.57	10.695%	$178.8499	$178.85	$178.85	$178.80
Purchase #5	$51.72	4.823%	$54.2145	$54.21	$54.20	$54.20
Purchase #6	$58.60	10.612%	$64.8186	$64.82	$64.80	$64.80
Purchase #7	$87.77	8.126%	$94.9022	$94.90	$94.90	$94.90
7 purchase totals =	$626.50		$676.5618	$676.56	$676.50	$676.50