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	$40.33	7.322%	$43.283	$43.28	$43.30	$43.30
Purchase #2	$69.30	10.161%	$76.3416	$76.34	$76.35	$76.30
Purchase #3	$41.72	4.537%	$43.6128	$43.61	$43.60	$43.60
Purchase #4	$64.37	4.279%	$67.1244	$67.12	$67.10	$67.10
Purchase #5	$90.80	5.487%	$95.7822	$95.78	$95.80	$95.80
Purchase #6	$157.77	9.431%	$172.6493	$172.65	$172.65	$172.60
Purchase #7	$80.65	9.355%	$88.1948	$88.19	$88.20	$88.20
7 purchase totals =	$544.94		$586.9881	$586.97	$587.00	$586.90