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	$165.28	12.178%	$185.4078	$185.41	$185.40	$185.40
Purchase #2	$15.49	10.617%	$17.1346	$17.13	$17.15	$17.10
Purchase #3	$114.38	13.379%	$129.6829	$129.68	$129.70	$129.70
Purchase #4	$165.90	3.680%	$172.0051	$172.01	$172.00	$172.00
Purchase #5	$69.86	3.643%	$72.405	$72.41	$72.40	$72.40
Purchase #6	$200.65	10.159%	$221.034	$221.03	$221.05	$221.00
Purchase #7	$85.32	3.526%	$88.3284	$88.33	$88.35	$88.30
7 purchase totals =	$816.88		$885.9978	$886.00	$886.05	$885.90