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	$157.38	13.805%	$179.1063	$179.11	$179.10	$179.10
Purchase #2	$113.36	13.570%	$128.743	$128.74	$128.75	$128.70
Purchase #3	$63.92	13.614%	$72.6221	$72.62	$72.60	$72.60
Purchase #4	$79.33	13.562%	$90.0887	$90.09	$90.10	$90.10
Purchase #5	$217.52	11.440%	$242.4043	$242.40	$242.40	$242.40
Purchase #6	$194.63	12.558%	$219.0716	$219.07	$219.05	$219.10
Purchase #7	$29.58	9.771%	$32.4703	$32.47	$32.45	$32.50
7 purchase totals =	$855.72		$964.5063	$964.50	$964.45	$964.50