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	$139.32	13.675%	$158.372	$158.37	$158.35	$158.40
Purchase #2	$159.33	5.860%	$168.6667	$168.67	$168.65	$168.70
Purchase #3	$165.80	10.227%	$182.7564	$182.76	$182.75	$182.80
Purchase #4	$168.82	4.439%	$176.3139	$176.31	$176.30	$176.30
Purchase #5	$169.83	9.810%	$186.4903	$186.49	$186.50	$186.50
Purchase #6	$222.31	9.870%	$244.252	$244.25	$244.25	$244.30
Purchase #7	$103.64	8.333%	$112.2763	$112.28	$112.30	$112.30
7 purchase totals =	$1,129.05		$1,229.1276	$1,229.13	$1,229.10	$1,229.30