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	$206.71	11.379%	$230.2315	$230.23	$230.25	$230.20
Purchase #2	$151.57	13.370%	$171.8349	$171.83	$171.85	$171.80
Purchase #3	$82.31	11.483%	$91.7617	$91.76	$91.75	$91.80
Purchase #4	$111.57	9.732%	$122.428	$122.43	$122.45	$122.40
Purchase #5	$72.36	5.168%	$76.0996	$76.10	$76.10	$76.10
Purchase #6	$223.39	13.445%	$253.4248	$253.42	$253.40	$253.40
Purchase #7	$139.79	9.772%	$153.4503	$153.45	$153.45	$153.50
7 purchase totals =	$987.70		$1,099.2308	$1,099.22	$1,099.25	$1,099.20