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	$54.71	13.615%	$62.1588	$62.16	$62.15	$62.20
Purchase #2	$60.28	11.617%	$67.2827	$67.28	$67.30	$67.30
Purchase #3	$32.64	12.493%	$36.7177	$36.72	$36.70	$36.70
Purchase #4	$78.28	10.857%	$86.7789	$86.78	$86.80	$86.80
Purchase #5	$160.37	13.473%	$181.9767	$181.98	$182.00	$182.00
Purchase #6	$217.79	12.240%	$244.4475	$244.45	$244.45	$244.40
Purchase #7	$140.27	12.677%	$158.052	$158.05	$158.05	$158.10
7 purchase totals =	$744.34		$837.4143	$837.42	$837.45	$837.50