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	$209.30	11.233%	$232.8107	$232.81	$232.80	$232.80
Purchase #2	$169.75	10.200%	$187.0645	$187.06	$187.05	$187.10
Purchase #3	$128.61	11.467%	$143.3577	$143.36	$143.35	$143.40
Purchase #4	$99.26	6.286%	$105.4995	$105.50	$105.50	$105.50
Purchase #5	$90.96	10.298%	$100.3271	$100.33	$100.35	$100.30
Purchase #6	$223.62	3.471%	$231.3819	$231.38	$231.40	$231.40
Purchase #7	$137.78	8.591%	$149.6167	$149.62	$149.60	$149.60
7 purchase totals =	$1,059.28		$1,150.0581	$1,150.06	$1,150.05	$1,150.10