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	$117.36	5.443%	$123.7479	$123.75	$123.75	$123.70
Purchase #2	$191.39	7.567%	$205.8725	$205.87	$205.85	$205.90
Purchase #3	$243.87	9.145%	$266.1719	$266.17	$266.15	$266.20
Purchase #4	$185.75	5.850%	$196.6164	$196.62	$196.60	$196.60
Purchase #5	$240.32	8.487%	$260.716	$260.72	$260.70	$260.70
Purchase #6	$41.50	11.146%	$46.1256	$46.13	$46.15	$46.10
Purchase #7	$191.42	4.219%	$199.496	$199.50	$199.50	$199.50
7 purchase totals =	$1,211.61		$1,298.7463	$1,298.76	$1,298.70	$1,298.70