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	$182.79	12.417%	$205.487	$205.49	$205.50	$205.50
Purchase #2	$7.73	4.250%	$8.0585	$8.06	$8.05	$8.10
Purchase #3	$66.48	12.661%	$74.897	$74.90	$74.90	$74.90
Purchase #4	$178.77	11.742%	$199.7612	$199.76	$199.75	$199.80
Purchase #5	$88.89	6.313%	$94.5016	$94.50	$94.50	$94.50
Purchase #6	$80.45	9.560%	$88.141	$88.14	$88.15	$88.10
Purchase #7	$77.58	10.211%	$85.5017	$85.50	$85.50	$85.50
7 purchase totals =	$682.69		$756.3480	$756.35	$756.35	$756.40