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	$218.69	5.501%	$230.7201	$230.72	$230.70	$230.70
Purchase #2	$219.58	10.418%	$242.4558	$242.46	$242.45	$242.50
Purchase #3	$165.58	8.596%	$179.8133	$179.81	$179.80	$179.80
Purchase #4	$70.42	8.628%	$76.4958	$76.50	$76.50	$76.50
Purchase #5	$86.63	5.549%	$91.4371	$91.44	$91.45	$91.40
Purchase #6	$95.69	10.627%	$105.859	$105.86	$105.85	$105.90
Purchase #7	$225.94	3.350%	$233.509	$233.51	$233.50	$233.50
7 purchase totals =	$1,082.53		$1,160.2901	$1,160.30	$1,160.25	$1,160.30