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	$188.37	4.436%	$196.7261	$196.73	$196.75	$196.70
Purchase #2	$72.68	3.623%	$75.3132	$75.31	$75.30	$75.30
Purchase #3	$19.29	9.178%	$21.0604	$21.06	$21.05	$21.10
Purchase #4	$152.91	10.464%	$168.9105	$168.91	$168.90	$168.90
Purchase #5	$169.56	13.379%	$192.2454	$192.25	$192.25	$192.20
Purchase #6	$223.91	4.433%	$233.8359	$233.84	$233.85	$233.80
Purchase #7	$228.44	11.149%	$253.9088	$253.91	$253.90	$253.90
7 purchase totals =	$1,055.16		$1,142.0003	$1,142.01	$1,142.00	$1,141.90