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	$158.31	6.621%	$168.7917	$168.79	$168.80	$168.80
Purchase #2	$122.30	12.786%	$137.9373	$137.94	$137.95	$137.90
Purchase #3	$148.52	11.716%	$165.9206	$165.92	$165.90	$165.90
Purchase #4	$100.53	3.330%	$103.8776	$103.88	$103.90	$103.90
Purchase #5	$225.45	7.282%	$241.8673	$241.87	$241.85	$241.90
Purchase #6	$155.74	6.521%	$165.8958	$165.90	$165.90	$165.90
Purchase #7	$145.62	10.593%	$161.0455	$161.05	$161.05	$161.00
7 purchase totals =	$1,056.47		$1,145.3358	$1,145.35	$1,145.35	$1,145.30