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	$161.31	3.261%	$166.5703	$166.57	$166.55	$166.60
Purchase #2	$184.92	7.829%	$199.3974	$199.40	$199.40	$199.40
Purchase #3	$148.27	5.803%	$156.8741	$156.87	$156.85	$156.90
Purchase #4	$146.58	6.703%	$156.4053	$156.41	$156.40	$156.40
Purchase #5	$149.65	11.855%	$167.391	$167.39	$167.40	$167.40
Purchase #6	$88.45	13.782%	$100.6402	$100.64	$100.65	$100.60
Purchase #7	$63.65	10.822%	$70.5382	$70.54	$70.55	$70.50
7 purchase totals =	$942.83		$1,017.8165	$1,017.82	$1,017.80	$1,017.80