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	$160.72	7.467%	$172.721	$172.72	$172.70	$172.70
Purchase #2	$134.27	8.451%	$145.6172	$145.62	$145.60	$145.60
Purchase #3	$22.49	12.624%	$25.3291	$25.33	$25.35	$25.30
Purchase #4	$179.52	5.357%	$189.1369	$189.14	$189.15	$189.10
Purchase #5	$39.48	10.599%	$43.6645	$43.66	$43.65	$43.70
Purchase #6	$196.38	9.553%	$215.1402	$215.14	$215.15	$215.10
Purchase #7	$97.29	4.758%	$101.9191	$101.92	$101.90	$101.90
7 purchase totals =	$830.15		$893.5280	$893.53	$893.50	$893.40