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	$149.80	7.482%	$161.008	$161.01	$161.00	$161.00
Purchase #2	$50.92	12.831%	$57.4535	$57.45	$57.45	$57.50
Purchase #3	$100.97	10.194%	$111.2629	$111.26	$111.25	$111.30
Purchase #4	$42.42	9.441%	$46.4249	$46.42	$46.40	$46.40
Purchase #5	$134.59	4.579%	$140.7529	$140.75	$140.75	$140.80
Purchase #6	$78.48	6.160%	$83.3144	$83.31	$83.30	$83.30
Purchase #7	$42.98	8.795%	$46.7601	$46.76	$46.75	$46.80
7 purchase totals =	$600.16		$646.9767	$646.96	$646.90	$647.10