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	$190.67	4.789%	$199.8012	$199.80	$199.80	$199.80
Purchase #2	$250.41	11.236%	$278.5461	$278.55	$278.55	$278.50
Purchase #3	$90.42	8.119%	$97.7612	$97.76	$97.75	$97.80
Purchase #4	$188.40	13.650%	$214.1166	$214.12	$214.10	$214.10
Purchase #5	$102.82	6.127%	$109.1198	$109.12	$109.10	$109.10
Purchase #6	$154.73	4.284%	$161.3586	$161.36	$161.35	$161.40
Purchase #7	$106.31	5.174%	$111.8105	$111.81	$111.80	$111.80
7 purchase totals =	$1,083.76		$1,172.5140	$1,172.52	$1,172.45	$1,172.50