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	$158.59	4.519%	$165.7567	$165.76	$165.75	$165.80
Purchase #2	$30.54	3.544%	$31.6223	$31.62	$31.60	$31.60
Purchase #3	$138.74	9.774%	$152.3004	$152.30	$152.30	$152.30
Purchase #4	$56.81	4.860%	$59.571	$59.57	$59.55	$59.60
Purchase #5	$142.88	13.210%	$161.7544	$161.75	$161.75	$161.80
Purchase #6	$25.37	10.590%	$28.0567	$28.06	$28.05	$28.10
Purchase #7	$18.84	3.418%	$19.484	$19.48	$19.50	$19.50
7 purchase totals =	$571.77		$618.5455	$618.54	$618.50	$618.70