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	$222.91	8.522%	$241.9064	$241.91	$241.90	$241.90
Purchase #2	$181.31	5.181%	$190.7037	$190.70	$190.70	$190.70
Purchase #3	$142.45	7.685%	$153.3973	$153.40	$153.40	$153.40
Purchase #4	$11.66	7.753%	$12.564	$12.56	$12.55	$12.60
Purchase #5	$92.52	10.257%	$102.0098	$102.01	$102.00	$102.00
Purchase #6	$211.55	13.828%	$240.8031	$240.80	$240.80	$240.80
Purchase #7	$165.69	12.147%	$185.8164	$185.82	$185.80	$185.80
7 purchase totals =	$1,028.09		$1,127.2007	$1,127.20	$1,127.15	$1,127.20