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	$91.66	11.172%	$101.9003	$101.90	$101.90	$101.90
Purchase #2	$96.70	9.416%	$105.8053	$105.81	$105.80	$105.80
Purchase #3	$238.65	7.230%	$255.9044	$255.90	$255.90	$255.90
Purchase #4	$168.73	4.678%	$176.6232	$176.62	$176.60	$176.60
Purchase #5	$115.31	4.831%	$120.8806	$120.88	$120.90	$120.90
Purchase #6	$170.71	4.751%	$178.8204	$178.82	$178.80	$178.80
Purchase #7	$111.61	3.273%	$115.263	$115.26	$115.25	$115.30
7 purchase totals =	$993.37		$1,055.1972	$1,055.19	$1,055.15	$1,055.20