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	$217.85	13.204%	$246.6149	$246.61	$246.60	$246.60
Purchase #2	$114.48	5.157%	$120.3837	$120.38	$120.40	$120.40
Purchase #3	$99.57	11.636%	$111.156	$111.16	$111.15	$111.20
Purchase #4	$154.49	11.766%	$172.6673	$172.67	$172.65	$172.70
Purchase #5	$53.55	4.623%	$56.0256	$56.03	$56.05	$56.00
Purchase #6	$175.58	3.759%	$182.1801	$182.18	$182.20	$182.20
Purchase #7	$242.34	11.113%	$269.2712	$269.27	$269.25	$269.30
7 purchase totals =	$1,057.86		$1,158.2988	$1,158.30	$1,158.30	$1,158.40