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	$217.39	3.670%	$225.3682	$225.37	$225.35	$225.40
Purchase #2	$30.73	3.388%	$31.7711	$31.77	$31.75	$31.80
Purchase #3	$123.38	3.188%	$127.3134	$127.31	$127.30	$127.30
Purchase #4	$61.25	13.298%	$69.395	$69.40	$69.40	$69.40
Purchase #5	$150.88	9.342%	$164.9752	$164.98	$165.00	$165.00
Purchase #6	$200.88	8.324%	$217.6013	$217.60	$217.60	$217.60
Purchase #7	$59.69	12.503%	$67.153	$67.15	$67.15	$67.20
7 purchase totals =	$844.20		$903.5772	$903.58	$903.55	$903.70