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	$94.50	12.810%	$106.6055	$106.61	$106.60	$106.60
Purchase #2	$178.55	3.693%	$185.1439	$185.14	$185.15	$185.10
Purchase #3	$79.87	8.247%	$86.4569	$86.46	$86.45	$86.50
Purchase #4	$36.64	10.314%	$40.419	$40.42	$40.40	$40.40
Purchase #5	$243.66	13.134%	$275.6623	$275.66	$275.65	$275.70
Purchase #6	$213.49	7.861%	$230.2724	$230.27	$230.25	$230.30
Purchase #7	$244.29	10.226%	$269.2711	$269.27	$269.25	$269.30
7 purchase totals =	$1,091.00		$1,193.8311	$1,193.83	$1,193.75	$1,193.90