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	$10.60	12.739%	$11.9503	$11.95	$11.95	$12.00
Purchase #2	$98.77	6.789%	$105.4755	$105.48	$105.50	$105.50
Purchase #3	$78.44	13.510%	$89.0372	$89.04	$89.05	$89.00
Purchase #4	$156.73	13.128%	$177.3055	$177.31	$177.30	$177.30
Purchase #5	$49.52	4.619%	$51.8073	$51.81	$51.80	$51.80
Purchase #6	$109.39	4.153%	$113.933	$113.93	$113.95	$113.90
Purchase #7	$92.71	13.293%	$105.0339	$105.03	$105.05	$105.00
7 purchase totals =	$596.16		$654.5427	$654.55	$654.60	$654.50