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	$109.51	6.186%	$116.2843	$116.28	$116.30	$116.30
Purchase #2	$171.79	12.261%	$192.8532	$192.85	$192.85	$192.90
Purchase #3	$112.64	4.502%	$117.7111	$117.71	$117.70	$117.70
Purchase #4	$231.89	10.225%	$255.6008	$255.60	$255.60	$255.60
Purchase #5	$108.35	9.434%	$118.5717	$118.57	$118.55	$118.60
Purchase #6	$84.56	5.306%	$89.0468	$89.05	$89.05	$89.00
Purchase #7	$200.94	11.502%	$224.0521	$224.05	$224.05	$224.10
7 purchase totals =	$1,019.68		$1,114.1200	$1,114.11	$1,114.10	$1,114.20