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	$122.35	4.667%	$128.0601	$128.06	$128.05	$128.10
Purchase #2	$31.74	8.558%	$34.4563	$34.46	$34.45	$34.50
Purchase #3	$144.42	5.323%	$152.1075	$152.11	$152.10	$152.10
Purchase #4	$219.25	7.411%	$235.4986	$235.50	$235.50	$235.50
Purchase #5	$78.67	6.286%	$83.6152	$83.62	$83.60	$83.60
Purchase #6	$199.77	11.554%	$222.8514	$222.85	$222.85	$222.90
Purchase #7	$156.53	4.254%	$163.1888	$163.19	$163.20	$163.20
7 purchase totals =	$952.73		$1,019.7779	$1,019.79	$1,019.75	$1,019.90