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	$235.43	4.377%	$245.7348	$245.73	$245.75	$245.70
Purchase #2	$19.72	5.531%	$20.8107	$20.81	$20.80	$20.80
Purchase #3	$50.44	6.721%	$53.8301	$53.83	$53.85	$53.80
Purchase #4	$228.84	11.335%	$254.779	$254.78	$254.80	$254.80
Purchase #5	$187.94	6.547%	$200.2444	$200.24	$200.25	$200.20
Purchase #6	$198.87	5.392%	$209.5931	$209.59	$209.60	$209.60
Purchase #7	$77.95	9.460%	$85.3241	$85.32	$85.30	$85.30
7 purchase totals =	$999.19		$1,070.3162	$1,070.30	$1,070.35	$1,070.20