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	$213.47	4.485%	$223.0441	$223.04	$223.05	$223.00
Purchase #2	$58.88	7.647%	$63.3826	$63.38	$63.40	$63.40
Purchase #3	$172.76	12.764%	$194.8111	$194.81	$194.80	$194.80
Purchase #4	$70.82	9.176%	$77.3184	$77.32	$77.30	$77.30
Purchase #5	$173.83	7.295%	$186.5109	$186.51	$186.50	$186.50
Purchase #6	$96.40	9.337%	$105.4009	$105.40	$105.40	$105.40
Purchase #7	$122.59	3.787%	$127.2325	$127.23	$127.25	$127.20
7 purchase totals =	$908.75		$977.7005	$977.69	$977.70	$977.60