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	$224.52	10.713%	$248.5728	$248.57	$248.55	$248.60
Purchase #2	$97.50	8.656%	$105.9396	$105.94	$105.95	$105.90
Purchase #3	$220.78	8.321%	$239.1511	$239.15	$239.15	$239.20
Purchase #4	$233.29	3.566%	$241.6091	$241.61	$241.60	$241.60
Purchase #5	$36.90	9.209%	$40.2981	$40.30	$40.30	$40.30
Purchase #6	$211.44	8.122%	$228.6132	$228.61	$228.60	$228.60
Purchase #7	$93.31	3.175%	$96.2726	$96.27	$96.25	$96.30
7 purchase totals =	$1,117.74		$1,200.4565	$1,200.45	$1,200.40	$1,200.50