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	$134.42	9.240%	$146.8404	$146.84	$146.85	$146.80
Purchase #2	$166.31	4.713%	$174.1482	$174.15	$174.15	$174.10
Purchase #3	$54.39	3.561%	$56.3268	$56.33	$56.35	$56.30
Purchase #4	$50.37	8.501%	$54.652	$54.65	$54.65	$54.70
Purchase #5	$167.79	3.795%	$174.1576	$174.16	$174.15	$174.20
Purchase #6	$123.91	3.494%	$128.2394	$128.24	$128.25	$128.20
Purchase #7	$138.80	8.492%	$150.5869	$150.59	$150.60	$150.60
7 purchase totals =	$835.99		$884.9513	$884.96	$885.00	$884.90