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	$73.48	4.835%	$77.0328	$77.03	$77.05	$77.00
Purchase #2	$56.48	8.380%	$61.213	$61.21	$61.20	$61.20
Purchase #3	$222.64	13.713%	$253.1706	$253.17	$253.15	$253.20
Purchase #4	$39.46	6.859%	$42.1666	$42.17	$42.15	$42.20
Purchase #5	$239.96	8.283%	$259.8359	$259.84	$259.85	$259.80
Purchase #6	$36.70	10.151%	$40.4254	$40.43	$40.45	$40.40
Purchase #7	$208.89	9.333%	$228.3857	$228.39	$228.40	$228.40
7 purchase totals =	$877.61		$962.2300	$962.24	$962.25	$962.20