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	$204.62	12.198%	$229.5795	$229.58	$229.60	$229.60
Purchase #2	$20.42	4.440%	$21.3266	$21.33	$21.35	$21.30
Purchase #3	$185.87	4.638%	$194.4907	$194.49	$194.50	$194.50
Purchase #4	$162.30	5.408%	$171.0772	$171.08	$171.10	$171.10
Purchase #5	$74.27	12.522%	$83.5701	$83.57	$83.55	$83.60
Purchase #6	$170.52	5.338%	$179.6224	$179.62	$179.60	$179.60
Purchase #7	$194.95	5.739%	$206.1382	$206.14	$206.15	$206.10
7 purchase totals =	$1,012.95		$1,085.8047	$1,085.81	$1,085.85	$1,085.80